USMLE Step 2 CK Medical Subject Review: Internal: Infectious Diseases

30-year-old woman presents with diabetic ketoacidosis and foot ulcers. The patient is treated with fluid replacement, potassium, insulin, and antimicrobials; the ulcers are debrided. On the 2nd day of treatment the glycemia is controlled, but the patient notes headache and facial pain. Examination shows a temperature of 38.5° C and a prominent black eschar on nasal mucosa. A diagnosis of an infection that is usually fatal within 48 - 72 hours is made. What is the disease?

Mucormycosis

A woman presents with a non-tender lesion on her tongue that she noticed a few days ago. Past medical history includes positive RPR "several years ago." Physical exam reveals the lesion is gray in color, raised, and oval-shaped. 3 similar patches are noted in her oral cavity. What is the most likely diagnosis?

Mucous patch due to syphilis

A healthy couple presents for an evaluation before traveling to the Dominican Republic; they leave in 1 month and will stay for 4 weeks. The CDC lists the Dominican Republic as a malaria-endemic area, but it is not considered to have a resistant strain of Plasmodium falciparum. What is the best advice for this couple?

"You should both take chloroquine weekly starting 1 week before travel."

6-month-old infant is brought in for routine vaccination. The mother saw information about a measles outbreak online. There is no known measles outbreak in the state. The mother is asking for more information about this vaccine. She would like her child to receive it now. What ages of administration are appropriate to advise the mother about for this vaccine?

12-15 months, 4-6 years

51-year-old man presents with what he describes as "fast, shooting pains" in his legs; he is also experiencing a slight tremor when he writes or eats. In the past, he has experienced an occasional URI, but he appears to be immunocompetent and has not required treatment for any infections subsequent to these viral syndromes. His past medical history does not include any significant neurological events, but the examination today reveals a loss of reflexes in his leg and bilateral Argyll Robertson pupils, pointing to a diagnosis of general paresis. How long after infection with Treponema pallidum would these symptoms manifest themselves?

10 to 20 years

24-year-old healthy woman complains of several days of urinary frequency and suprapubic pain, particularly with voiding. She denies previous similar symptoms. She is sexually active and uses condoms and spermicide. She takes no medications and has no allergies. She appears well and has a normal exam. Her urinalysis shows: Glucose none Blood trace Protein trace Cells 15 white cells, 2 red cells/high powered field Casts none Leukocyte esterase, nitrite positive, positive Culture pending How should you treat her urinary symptoms?

3 days oral trimethoprim/sultamethoxazole

31-year-old HIV-positive woman presents for ongoing care. She was diagnosed with HIV 2 years ago, and she began antiretroviral therapy. Her CD4 T cell count is 400 cells/mL, and she has a history of oral candidiasis. As part of her evaluation, a tuberculin skin test (TST) is performed using 5 TU of purified protein derivative (PPD). The test site is examined 48 hours later and the skin reaction is measured. What is the minimum diameter of induration at which this test result should be considered positive in this patient?

5 mm

30-year-old woman presents with a 1-week history of sores on her genitals. On examination, you note a solitary ulcer on her labia; it has a velvety base and bleeds easily. Her inguinal and femoral nodes are not palpable. What is the most likely diagnosis?

Donovanosis

32-year-old man presents with bilateral blurred vision and a large number of "floaters." The patient is HIV-positive and has experienced failure of long-term highly active antiretroviral therapy (HAART). His CD4+ T cell count is 50 cells per mm2. Fundoscopy shows white exudates around the retina with peripheral hemorrhages. What treatment would be most appropriate for this patient?

Ganciclovir

A 41-year-old man presents with a sore on his jaw. History reveals that the patient is currently undergoing chemotherapy for lymphoblastic leukemia. Examination reveals normal vital signs. The patient has a 1 cm diameter mass on his jaw; the lesion is painful and purulent. Gram stain of the exudate shows a slender Gram-positive filamentous organism with an abundance of yellow crystals. Culture confirms the diagnosis as an anaerobic organism. What is the likely cause of the patient's lesion?

Actinomyces

15-year-old patient presents with a swollen hand that appears to be infected. Vital signs are normal and the patient appears otherwise healthy. There is no fever and the patient does not report any occurrence of chills. The patient cut his hand with a piece of glass 3 days prior. At the wound site there is a raised area surrounded by a zone of erythema; there is some exudate present. The wound is drained and the material is sent for Gram stain and culture. The Gram stain exhibits moderate numbers of white blood cells and Gram-positive rods that appear to 'line-up' and are pleomorphic. The culture is positive for 4+ Gram-positive rods with the following characteristics: CULTURE TEST Result Growth on aerobic blood agar Pinpoint beta-hemolytic Growth on aerobic chocolate agar Pinpoint Growth on MacConkey Neg Growth on anaerobic blood agar Medium-sized colonies with a wide zone of beta-hemolysis Hydrolyze gelatin Pos Catalase Pos Motility Neg What is the most probable cause of infection in this patient?

Actinomyces (Corynebacterium) pyogenes

7-year-old girl presents with lethargy, weakness, unsteady gait, and inability to walk. Her symptoms started the morning of presentation. Prior to that, the child was normal. There is no history of trauma and no previous medical conditions. The child is conscious, but she is not oriented to time or place. Her temperature is 99°F. Pulse is 98/min, BP is 100/60 mm Hg, and RR is 14/min. A lumbar puncture reveals no WBCs; spinal fluid protein is 22 mg/ml, and a bacterial culture reveals no growth. Serum blood glucose level is found to be decreased. What is the most likely etiology of her condition?

Acute intoxication

A previously healthy 5-year-old boy presents with complaints of bilateral eye pain and redness. The child's mother reports that several children in his daycare facility have had similar symptoms. Results of physical exam indicate bilateral nonsuppurative conjunctival inflammation, photophobia, and preauricular lymphadenopathy. What is the most likely organism responsible for this outbreak of conjunctivitis?

Adenovirus

A woman diagnosed with mild pelvic inflammatory disease is given oral medication for treatment, but the patient presents the next day with severe nausea, vomiting, and a high fever. What is the next step in the management of this patient's disease?

Admit the patient to the hospital to initiate parenteral therapy.

60-year-old man with history of heavy smoking and moderately severe chronic obstructive pulmonary disease (COPD) has been feeling weak recently. He notes a 3- to 4-day history of cough, chills, pleuritic chest pain, and low-grade fever. Chest X-ray shows a small dense infiltrate in the right lower lobe. Gram stain of the patient's sputum reveals numerous gram-negative cocci, many of which occur in pairs. What is the most appropriate treatment?

Amoxicillin and clavulanic acid

72-year-old man presents with low-grade fever, nausea, confusion, and lethargy. His past medical history is significant for hypertension, hypercholesterolemia, and diabetes. He had sinusitis approximately 1 week ago; otherwise, he has been healthy. Laboratory workup shows a CSF with elevated opening pressure and low blood glucose levels. A Gram stain on the CSF shows gram-positive cocci. CBC shows an elevation of PMNs, but it is otherwise normal. What is the most appropriate treatment in this case?

Antibiotic therapy

10-year-old girl presents with chest pain and joint aches. Her mother says that about 2 weeks ago, her daughter had a sore throat with fevers and pus around her tonsils. She was prescribed a 14-day course of penicillin on the initial visit, but her mother stopped the medications after 2 days because the fever subsided. She also experienced chest pain and recurrence of fever. Her vital signs: blood pressure 120/80 mm Hg, heart rate 110 beats/min, temperature 102.3°F. On physical examination, normal S1/S2 and a II/VI short mid-diastolic murmur are heard. Her EKG shows a sinus tachycardia with a prolonged PR interval. What would have been the best way to prevent this disease?

Antibiotic compliance

31-year-old female nurse who works at a local hospital presents with a purpuric rash covering her arms, legs, and abdomen, as well as fever, chills, nausea, abdominal tenderness, tachycardia, and generalized myalgias. Prior to the development of the rash, the patient noted that she had a headache, cough, and sore throat. Laboratory studies were positive for gram-negative diplococci in the blood, along with thrombocytopenia and an elevation in PMNs. Urinalysis showed blood, protein, and casts. Vital signs are as follows: BP 92/66, P 96, RR 14, T 39. The patient denies any foreign travel and does not have any sick contacts. She is admitted to the hospital and placed in respiratory isolation. What major course of therapy should this patient receive?

Antibiotics

14-month-old girl presents in the middle of the night. Her mother tells you that she has been fussy and has not been feeding well for the past 48 hours. In the last 4 hours, she has developed a high fever; it was 102 degrees Fahrenheit when measured at home. Her mother also notices that the child appears reluctant to move her right leg; the girl appears to keep it rotated outward. Examination reveals a distressed, febrile child. Her cardiovascular, abdominal, and respiratory exams appear normal. Her right leg is held fixed in external rotation and partial flexion, with minimal hip joint effusion. A needle aspirate of the joint fluid reveals the following; WBC count - 60,000/cc, neutrophils 95% No crystals Gram stain is positive for Gram-positive cocci in clusters. What is the most important step in preventing destruction of the joint?

Arthrotomy and irrigation of joint space

60-year-old man presents with a 1-year history of increasing dyspnea. The patient used to work as a construction worker, and he is a chronic smoker. A chest radiograph shows diaphragmatic pleural plaques and interstitial lung disease. What is the most likely diagnosis?

Asbestosis

During a routine X-ray examination for employment insurance purposes, the radiologist notices a rounded lesion in a pulmonary cavity on the right upper lobe of the pulmonary X-ray of a middle-aged man. The patient was treated for pulmonary cavitary tuberculosis (TB) 2 years ago; he has completed treatment, and he has not had any problems since. What late complication of TB is seen in this patient?

Aspergilloma

70-year-old male is brought to your emergency room with a pulse of 35 beats per minute. His electrocardiogram reveals a complete heart block. Implantation of a permanent cardiac pacemaker is followed by a chronic low-grade fever. His febrile (fever) hospital-acquired complication is most probably due to

Aspergillus fumigatus

26-year-old gravida 2 para 1 woman is being followed during her pregnancy. Her medical history is significant for late latent stage of syphilis for which she is under stage-specific treatment. What is seen in a case of late latent syphilis?

Asymptomatic patient with positive serologic evidence of syphilis

17-year-old sexually active G1P0 at week 18 of her pregnancy presents with vaginal discharge. Upon vaginal examination, cervical purulent discharge is visualized. Cultures and gram stain do not reveal any organisms. The patient is diagnosed with Chlamydia trachomatis infection. What is the medication of choice for her condition?

Azithromycin

18-year-old woman presents with a 1-week history of vaginal discharge that has become progressively worse. She reports recent unprotected intercourse. On exam, the white discharge appears watery and she exhibits cervical motion tenderness. A KOH wet prep is negative without clue cells or hyphae. What is the most appropriate treatment?

Azithromycin

22-year-old male college student presents with a 2-week history of low grade fever, sore throat, dry cough, and chest wall discomfort from coughing. He is on no medications, but he has a history of mild asthma not requiring chronic therapy. He has been under a lot of pressure at work and has not been sleeping well. He is concerned he might have pneumonia. Vitals include a temperature of 100.6°F, BP of 126/76 mm Hg, pulse of 82 beats/min, and RR of 20/min. Lung exam reveals coarse rhonchi throughout the lung fields, with rales in the right lower lobe and egophony demonstrated over the right lower lobe. The results of a PA and lateral chest X-ray reveal right lower lobe infiltration. What is the best empiric medication for this patient's illness?

Azithromycin 500 mg first dose, then 250 mg daily for 4 days

24-year-old woman presents for follow-up 7 days after a medical abortion with mifepristone and misoprostol; she has a fever, chills, and abdominal pain. Examination shows a temperature of 38°C, tachycardia, slight vaginal bleeding, and sanguinopurulent cervical discharge. Blood cultures are negative, and pre-existing Chlamydia trachomatis is suspected. What is the best course of action for this patient?

Azithromycin with ceftriaxone

44-year-old male salesperson presents after driving cross-country in a rural part of southern Ohio. His car had broken down and he found a local farmer who let the salesman spend the night in his farmhouse. His car was repaired the next day, and he promptly returned home. Several weeks later, he experienced an abrupt onset of a fever, non-productive cough, shortness of breath, and mild chest pain. Believing he has just caught a cold, the salesman thinks nothing of it. A few days after the onset of symptoms, he is much better, but he presents to your office for an opinion. You order a CXR that reveals airspace consolidations. What is the most likely cause of his symptoms?

Blastomycosis

60-year-old man is diagnosed with bacterial pneumonia with extensive involvement of the right upper and lower lobes. The patient reports shortness of breath when lying on his right side. An ABG drawn in this position shows a PaO2 of 43 mm Hg, while an ABG drawn when lying on his left side reveals a PaO2 of 67 mm Hg. What would explain the decrease in PaO2 when the patient is lying on the right side?

Blood flow to the right lung increases when it is in the dependent position.

A 4-year-old patient presents with a 1-week history of violent coughing spells that lead to the child turning red and gasping for air as if choking. Vomiting also accompanies some of these choking episodes. The patient appears agitated and fatigued. Respiration and pulse are elevated (75/min and 150 beats/min respectively). A chest radiograph is ordered, and the results are insignificant. A CBC is ordered, and it produces the results that are listed in the table. A nasopharyngeal swab is sent to the laboratory for direct fluorescent antibody staining for the suspected organism, and it is found to be positive. 3 days later, culture results are also positive for the same organism. This child has the classic presentation, and laboratory results confirm it; what is the diagnosis that explains the cough?

Bordetella pertussis

37-year-old HIV positive man with a CD4 count of 200/μL visits an internal medicine clinic presenting with diarrhea. He describes a headache and myalgia followed by 10 days of mild to moderate abdominal cramps, tenesmus, and several loose stools daily. On examination, the patient is found to have normal vital signs and periumbilical tenderness. Fecal examination shows leukocytes and occult blood. Routine stool cultures are positive for microaerophilic, slightly curved, Gram-negative rods that grow at 42°C. What is the most likely organism causing this patient's illness?

Campylobacter jejuni

36-year-old woman presents with vaginal discharge. She has a history of itching and white discharge. She is sexually active with her husband only. She takes oral contraceptive pills for contraception, and she has never been diagnosed with an STD (sexually transmitted disease). On examination, the vagina is hyperemic and covered with white cottage cheese-appearing discharge. What is the most likely diagnosis?

Candida vaginitis

23-year-old man presents with a 2-day history of a red, swollen, and painful right knee. The pain and swelling have steadily progressed since they began. He has been feeling feverish for the last few hours. He admits to having unprotected sexual intercourse with multiple women over the past few months. On examination, temperature is 100.4°F (38°C) and BP is 110/70 mm Hg. Cardiovascular, respiratory, and abdominal exams are normal. Right knee demonstrates clinical signs of an effusion, with severe tenderness and surrounding muscle spasm. An aspirate of the joint fluid yields the following findings: WBC count 60,000/cc, neutrophils 95% No crystals Gram stain is negative Synovial fluid culture: Gram-negative diplococci on Thayer-Martin media Considering the most likely diagnosis, what is the most appropriate pharmacotherapy?

Ceftriaxone

21-year-old college student presents with headache, fever, lethargy, and somnolence. Medical history reveals a recent upper respiratory infection and treatment for alcohol-dependence syndrome. Examination reveals a temperature of 39° C; a lumbar puncture shows lancet-shaped Gram-positive cocci. The region where the student resides has a high prevalence of penicillin-resistant pneumococci. Pending culture results, what is the appropriate empiric antimicrobial therapy?

Ceftriaxone and vancomycin

5-year-old African American girl with sickle cell disease presents due to right leg pain. She began to experience right thigh pain and a slight limp following a playground injury 2 weeks ago. Upon sustaining the injury, she was taken to a local ER; X-rays were negative for evidence fracture. She was diagnosed with and treated for a leg contusion. Over the past 2 weeks, the pain has become more severe and she has experienced fever; temperatures have been as high as 102°F, and she has experienced episodic chills. On physical examination, her temperature is 101°F; her right leg is swollen, tender, and erythematous over the anterior aspect of the thigh. The remainder of the PE is unremarkable. CBC with differential reveals a leukocytosis; there is a predominance of neutrophils and a bandemia. What is the most appropriate empiric treatment?

Ceftriaxone and vancomycin

12-year-old girl visits a dermatology clinic presenting with itching and a 5-day history of rash. Her mother reports that they returned the previous day from a trip to Louisiana where the family camped on the beach. During their visit, her 2 children received numerous insect bites and found ticks on their clothing. The girl's 7-year-old brother also has a rash. Examination is unremarkable except for an erythematous macular rash with urticarial and papular patches. The rash extends from the ankles to the lower trunk and is absent on the face and hands. What is the most likely diagnosis?

Cercarial dermatitis

22-year-old male off-shore medical student presents with a 2-day history of dysuria accompanied by a painful genital lesion that has formed into an ulcer. He also reports fever with a recorded oral temperature of 101°F, generalized malaise, myalgias, and headache. He denies lesion blistering, and there is no previous history of this condition. He has otherwise been in good general health. He is heterosexual and admits to multiple sexual partners in the recent past with inconsistent use of condoms. T=100.9°F; BP=130/80; P=70; RR=12. Pertinent findings on the physical examination are relegated to the genital exam. Exam reveals a non-circumcised penis with a non-indurated ulcer of the penile frenulum and foreskin, sharply defined borders, undermined edges, and purulent yellow-gray exudative discharge. There is bilaterally tender inguinal adenopathy. Testicles are descended bilaterally with no lesions or masses. What is the most likely diagnosis?

Chancroid

30-year-old woman presents with a 1-week history of very painful sores on her genitals. On examination, you note multiple ulcers on her labia; they have purulent bases and are associated with unilateral inguinal lymphadenopathy. What is the most likely diagnosis?

Chancroid

45-year-old woman received an orthotopic cardiac transplant 3 months ago. She has had acute mild rejection treated with increasing immunosuppressive therapy. She has developed a cough with fever and headache. A chest X-ray reveals consolidation involving the right mid-lung. A bronchoalveolar lavage reveals long filamentous Gram-positive organisms. What would be the most likely cause of the consolidation?

Chronic abscessing pneumonia

You see a 35-year-old African American male for a painless tumor on his left hand. He also complains about malaise, headache, fever, and nausea. He works at a textile mill, which processes imported goat hair. He reports having cut himself about a week earlier at work. The lesion is a red-brown papule with peripheral edema, vesiculation, and induration. It shows an ulcer and formation of black eschar in the center. What is the proper treatment?

Ciprofloxacin

34-year-old man presents with a fever. The patient has been HIV positive for at least 5 years and presently has a CD4 T-cell count of 55 cells/μL. Examination reveals a temperature of 39° C, and laboratory results show an elevated alkaline phosphatase and hemoglobin of 6 g/dL. Blood cultures are positive for acid-fast bacilli which are identified as Mycobacterium avium-intracellulare. What is the most appropriate therapy for this patient?

Clarithromycin and ethambutol

45-year-old woman is brought to the ED via ambulance; she is accompanied by her very anxious husband. He reports that she has been vomiting for several hours, and she has complained of acute abdominal pain and blurred vision after eating home-canned green beans. Examination reveals dilated pupils, diplopia, acute paralysis of the upper limbs, and respiratory distress. Subsequent analysis reveals the cause to be botulism. In reported cases of botulism, each of the ill persons had consumed food that was improperly handled. What statement abou botulism is true?

Clostridium botulinum spores are present in soil

35-year-old man was admitted to the hospital 10 days ago for shortness of breath. He has chest X-ray showing lower lung consolidation and was diagnosed with pneumonia. He was treated with intravenous antibiotics and now his symptoms are resolving and his X-ray showed improvement but he is now complaining of abdominal cramps and diarrhea. The most likely diagnosis is

Clostridium difficile colitis

40-year-old diabetic man presents with pain in his left toe. Physical examination reveals a discolored large toe; there is a blackened area surrounded by a metallic gray, edematous area, and a red peripheral area. Material is obtained for Gram stain and culture, and the patient is referred for surgical debridement of the area. The Gram stain is significant for a few Gram-positive rods. The culture is subsequently positive for a Gram-positive rod that has the following culture test results: CULTURE TEST Result Growth on aerobic blood agar Neg Growth on aerobic chocolate agar Neg Growth on aerobic MacConkey agar Neg Growth on anaerobic blood agar Pos (beta-hemolytic) Gram stain Gram-positive rods Spore formation Pos (subterminal) Lecithinase Pos Nitrate Pos Indole Neg Urease Neg Motility Pos What is the name of this organism?

Clostridium novyi

36-year-old male soybean farmer presents with the inability to walk. The patient reports having received a puncture wound on his left foot several days earlier; it became infected and bloated. Examination of the foot reveals a deep, highly purulent wound that has necrotized and produces a foul odor. The wound is drained and irrigated, and a wet mount of exudate is examined microscopically. Numerous motile rods containing terminal endospores with a 'tennis racket' appearance are seen. What organism is most likely responsible for the infection?

Clostridium tetani

A 6-year-old male had swelling on the right side of his cheek after a couple days of fever, malaise, and anorexia. He complains of discomfort while chewing and speaking. His father is very anxious and does not remember if he had this childhood disease. He seeks reassurance that he is not going to get the infection, and he asks if he will need an injection to prevent it. Which test is the best test to confirm that he had this illness before and that he is immune?

Complement Fixation test to detect of antibodies to envelope antigen (V antigen)

30-year-old woman presents with growths on her vagina. Physical examination shows raised, pedunculated, pink swellings that are found on the labia majora and perineum. She reports that the lesions are not painful. The patient is in a long-term relationship with a man, and she states that they always use condoms. What is the most likely diagnosis?

Condylomata acuminata

28-year-old man presents with a rash that began on his nose a few days ago. He states that it was very painful, red, and itchy initially; small blisters then began to form 1 day later. On physical examination, you appreciate a linear rash on the edge of the nose and on the tip of the nose. There is redness, small vesicles, and crust formation noted. Since there is involvement of the tip of the nose, you examine him thoroughly to exclude concurrent involvement of what structure?

Cornea

56-year-old man presents with type II diabetes and cellulitis. The patient is given a urinary catheter due to retention of urine. The patient is afebrile and his urine is brownish, ammoniacal, and contains particulate matter suggestive of crusting cystitis. A urine culture yields diphtheroids. What is the likely organism responsible for the patient's cystitis?

Corynebacterium urealyticum

70-year-old woman who is a nursing home resident with diabetes has been weak and febrile today. She has wet more than usual adult diapers. Her appetite and fluid intake are normal and her fingerstick blood glucose levels have been 90mg/dl. Her temperature is 99 degrees Farenheit. Her blood pressure is 119/79 mm hg. She has a normal neurological and lung exam and no hot joints. She has bilateral below the knee amputations. Her dipstick urinalysis shows no protein or glucose, trace blood positive leukocyte esterase, and positive nitrite. What is her most likely diagnosis?

Cystitis

34-year-old man presents with a 3-day history of fever, cough, and dyspnea. The chest X-ray shows bilateral perihilar infiltrates. The bronchoalveolar lavage reveals cysts of Pneumocystis carinii. What laboratory test finding is most likely to be present in this patient?

Decreased CD4 lymphocyte count

17-year-old sexually active G1P0 in her 32nd week of pregnancy develops a painful ulcer in her vaginal area. The ulcer has a friable base covered with a gray exudate. She also is experiencing tender lumps in her inguinal area on the right side. The border of the ulcer is punctured, and a sample is visualized using gram stain. Gram-negative streptobacilli are identified, which is consistent with Haemophilus ducreyi infection. HSV and syphilis screening comes back negative. Her physician prescribes ceftriaxone. What is one of the side effects of the medication used to treat her condition?

Diarrhea

25-year-old Caucasian male landscaper presents with a 2-week history of generalized malaise and an "unusual rash" on his right thigh. The patient reports that this rash has been widening, but he denies any pruritus or pain in association with his complaints. In the past week, he has also noticed a constant headache and mild fever. The past medical history is unremarkable. The physical exam reveals vital signs within the normal limits, enlarged non-tender diffuse lymph nodes in cervical and inguinal areas, and an erythematous rash with central clearing and few satellite lesions. Given this patient's diagnosis, how would this patient's clinical stage be defined?

Early localized

A mother brings her child to the ED after finding she could not awaken her this morning. History includes what the mother describes as "a blank staring" episode yesterday during which the child appeared to not respond to her mother's voice, but which resolved within a few minutes. Examination reveals a febrile child (1030 F) who is very difficult to arouse and, when aroused, cries and asks to be "left alone." As you suspect viral encephalitis, you know that a wide range of prognoses exists for different types of encephalitis. Which of the following types of arthropod-borne encephalitis has the worst prognosis?

Eastern equine

40-year-old man presents with fever, weakness, and pain in the right hand. Fever and weakness started this morning. 2 days ago, he noticed painful itching blisters on his hand. He thinks it might have been caused by a spider bite. He has type 2 diabetes mellitus and was treated in the ER for acute alcohol intoxication twice over the last month. His records show that he received a tetanus booster dose 5 years ago. On examination, he appears very ill; his blood pressure is 85/55 mm Hg, HR is 120/minute, and respiratory rate is 22/min. His hand is swollen and red; there is a small deep ulcer surrounded by a blue halo with preserved voluntary movements of the hand and fingers. Crepitus and discharge of fluid that resembles "dishwater" is observed. Laboratory findings: Test Result Reference Range Units Urine glucose Positive 0 Urine myoglobin Positive 0 Glucose 250 140 mg/dL BUN 256 1.8-71 mmol/L Blood alcohol levels 0.02 0 % by vol. WBC 25,000 4,500-10,000 per cubic mm Neutrophils 68 54-62 % Lymphocytes 24 24-44 % CRP 1000 1 mg/L Serum creatinine 2.6 0.7-1.3 mg/dL Serum potassium 6 3.5-5.2 mEq/L Serum sodium 137 135-147 mEq/L What is the next step in management of this patient?

Emergent surgical debridement

40-year-old woman presents with a 1-week history of abdominal pain and diarrhea. She reports that her stool is blood-stained and mucoid. A stool examination reveals trophozoites and Charcot-Leyden crystals. What is the causative organism?

Entamoeba histolytica

9-year-old girl presents with a 4-day history of malaise, muscle aches, headache, and fever. Her fevers have averaged 38.5°C. Of significance is the presence of a facial rash that has a 'slapped cheek' appearance. There is some presence of the same rash on the extremities. Because of the known increased incidence of fifth disease within the community, serum is collected for fifth disease titers. The patient is sent home with a future follow-up scheduled. The results of the titers are positive for active fifth disease. The rash found in the child is characteristic of the most likely diagnosis. What is it called?

Erythema infectiosum

16-year-old boy presents with a dry cough of 1-week duration, pharyngitis, and malaise. Examination shows a low-grade fever (38.5°C), and chest auscultation reveals sibilant rhonchi. Chest films show a patchy bronchopneumonia. What is the best course of treatment for this clinical picture?

Erythromycin

22-year-old woman at 24 weeks gestation presents with a 3-day history of a nonproductive cough and fever. She states she has been battling an upper respiratory infection that does not seem to go away. Initially, she thought that she had a cold, but the symptoms persisted. She was told by her obstetrician that she has the flu and to drink plenty of fluids and get some rest. Vital signs reveal temperature 101.2°F, blood pressure 120/80 mm Hg, heart rate 110/bpm, and respiratory rate 22 breaths/min. On physical examination, she appears ill; lungs exhibit wheezing. What would be an appropriate treatment for this patient?

Erythromycin

23-year-old woman presents with frequent and painful urination and lower back pain. History and physical exam reveal suprapubic pain, no evidence of systemic illness or fever, and no history of hospitalization. A presumptive diagnosis of a urinary tract infection (UTI) is made, and a urine culture yields lactose-fermenting beta-hemolytic gram-negative rods. What is the most likely etiology of the UTI?

Escherichia coli

60-year-old man presents to an urgent care center with complaints of painful urination, slight fever, and hematuria that began yesterday. He denies ever having such symptoms. His medical history is significant for hypertension, but this has been under control and he has been feeling well. He denies any recent travel or illness and has not had any sexual contact within the last month. His vital signs are as follows: Blood pressure 140/84 mmHg, pulse 74/min, respiration rate 12 per minute, temperature 99.6°F. The most likely organism causing this condition is

Escherichia coli

30-year-old man presents with a 2-month history of coughing and a 2-day history of coughing blood. He has been losing weight and sweating at night. On physical examination, the patient appears wasted and tachypneic with bronchial breath sounds in the right upper lobe and crepitations in the left upper lobe and right mid-zone. His direct sputum result comes back positive for acid-fast bacilli with Ziehl-Neelsen stain. His sputum is sent for culture and treatment is started for his condition. After starting the medication, he notices he is unable to distinguish between red and green colors. What treatment medication for his condition would cause this?

Ethambutol

45-year-old man came to the clinic complaining of a sudden blurring of vision that started a week ago. On examination, he was found to have a vision of 10/20 in the right and 20/20 in the left. His right eye also showed defective color vision, and he describes colors as washed out. He has never previously had problems in his eyes. He works in an assisted living house for elderly, and he was PPD converted to positive 4 months ago. He was started on Ethambutol, INH,and Rifampicin as recommended by his physician. What most probably has caused the patient's problem?

Ethambutol

45-year-old patient is being treated for tuberculosis. She is experiencing central scotomata, a loss of green-red color perception, and decreased visual acuity. What agent is most likely responsible?

Ethambutol

A 24-year-old man is brought to the emergency room in shock. A quick history from his girlfriend reveals that he has had a "blister on his left foot" for the past couple of days. According to the girlfriend, the patient developed a fever earlier in the day; he felt weak and eventually collapsed. He last passed urine the evening prior to presentation. On examination, his BP is 70/40 and pulse is 130/minute; his hands feel cold and clammy. Except for a swollen left foot, systemic examination is normal. His lab values are as follows: Total WBC count: 21,000/mm3Neutrophils: 55%Lymphocytes: 25%Hemoglobin: 11.0 g/dLCRP: 165 mg/LSerum Creatinine: 2.3 mg/dLUrine Myoglobin: positiveSerum K: 5.9 Meq/dLSerum Na: 133 Meq/dLECG: sinus tachycardia What is the critical component in management of this patient?

Extensive early surgical debridement

23-year-old pregnant woman visits a neighborhood clinic presenting with fever and a rash. It has been 14 weeks since her last menstrual period, and she has not received any prenatal care. Examination shows that the woman has a low-grade fever and numerous vesicular lesions on her face, neck, and abdomen. Based on immune history and exposure, a diagnosis of chickenpox is made. What statement is most true about this case?

Fetal infection at this stage of development may damage limbs and eyes

36-year-old woman presents with vaginal discharge. She has a history of itching and white discharge. She is sexually active with her husband only. She takes oral contraceptive pills for contraception, and she has never been diagnosed with an STD (sexually transmitted disease). On examination, the vagina is hyperemic and covered with white cottage cheese-appearing discharge. What is the treatment of choice?

Fluconazole

38-year-old man presents with a 3-day history of diarrhea. It is associated with bloating and nausea. He had been hiking in the woods, drinking untreated water from streams. Examination of the stool reveals cysts and trophozoites, but no leukocytes. What is the causative organism?

Giardia lamblia

55-year-old woman presents with a slight cough she has had for about a week. She is a nonsmoker, and she does not remember having a fever or feeling sick. The patient currently works as a third-grade teacher and has done this for 30 years. She has no past medical history of significant pulmonary diagnoses. Auscultation of the chest reveals clear lung fields. A chest X-ray shows a subpleural "coin lesion" in the right upper lobe. What is the most likely diagnosis?

Granuloma

45-year-old man presents with increasing cough and dyspnea over several months. He has also had increased serum urea, nitrogen, and serum creatinine. A chest X-ray shows multiple bilateral small nodules. A transbronchial biopsy shows necrotizing granulomatous inflammation involving small peripheral arteries. What is the most likely diagnosis?

Granulomatosis with polyangiitis (GPA)

35-year-old man with HIV comes to your office for follow up. At his last visit, his viral load was 2000 copies/ml and his CD4 count was 500 cells/ml, so no therapy was initiated. His urinalysis was normal at that time. He has no infectious symptoms. Today, his blood pressure is 129/80 mmHg, his retinal, cardiac, and pulmonary exams are normal, but he has bilateral +2 pitting pedal edema.Diagnostic studies show: Urinalysis pH 6, specific gravity 1.020, proteinuria 3 gm/24 hours no white cells, 2 non-dysmorphic red cells/high powered field, 1 fatty cast/high powered field Serum creatinine 1.4 mg/dl Liver function tests Normal Electrocardiogram Normal sinus rhythm Renal ultrasound Bilateral increased renal size, no masses, no hydronephrosis CD4 count 250 cells/ml Viral load 100,000 copies/ml Hepatitis B and C antibodies Negative ANA, double stranded DNA, complements 3 and 4 All normal Serum albumin 3.8 g/dl Whole blood glucose 80 mg/dl What is his most likely diagnosis?

HIV associated nephropathy

A 55-year-old woman presents with a several-month history of increasing cough and dyspnea. She also has increased serum urea, nitrogen, and serum creatinine. A chest X-ray shows multiple bilateral small nodules. A renal biopsy shows a focal necrotizing vasculitis; her antineutrophil cytoplasmic autoantibody (ANCA) test is positive at 1:160. What additional finding would be most likely to occur?

Hemoptysis

A 24-year-old woman presents after a 3-day history of fever, headache, and vomiting. Her roommate reports that the patient first described smelling strange odors, and she then could not remember where she was or her name. Examination reveals an aphasic patient with a temperature of 39°C. A lumbar puncture finds clear cerebral spinal fluid (CSF) with elevated opening pressure, elevated WBCs (92% lymphocytes), 1000 mg/dL protein, normal glucose, and a negative CSF Gram stain. CBC of the peripheral blood is normal. Phenytoin (Dilantin) is prescribed after the patient develops seizures. An MRI reveals significant edema and necrosis of the left temporal lobe, with involvement of the left basal ganglia. What is the most likely pathogen in this case?

Herpes simplex virus

35-year-old woman presents with a painful swelling of her left eyelid. On physical exam, there is tenderness to palpation and erythematous swelling present on the lid margin involving the eyelashes. What is the most likely diagnosis?

Hordeolum

A 32-year-old previously healthy man presents with edema. His blood pressure is 118/78 mmHg and the remainder of his exam is normal. Work up shows HIV. His CD4 count is 300 cells/ml and his viral load is 100,000 copies/ml. Urinalysis pH 6, specific gravity 1.020, 4g/day proteinuria no white cells, 2 non-dysmorphic red cells/high powered field, 1 fatty cast/high powered field Serum creatinine 1.4 mg/dl Liver function tests Normal Electrocardiogram Normal sinus rhythm Renal ultrasound Bilateral increased renal size, no masses, no hydronephrosis CD4 count 250 cells/ml Viral load 100,000 copies/ml Hepatitis B and C antibodies Negative ANA, double stranded DNA, complements 3 and 4 All normal Serum albumin 3.4 g/l Whole blood glucose 80 mg/dl Serum and urine protein electrophoresis normal Renal biopsy Focal collapsing segmental glomerulosclerosis with tubular microcysts Which is the best initial therapy?

Highly aggressive antiretroviral therapy

2-year-old boy is being evaluated for persistent (greater than 14 days) fever. Symptoms are non-specific and no cause has been determined. What role would administration of antipyretic medication have for this patient's febrile illness?

His response will be improved patient comfort

30-year-old man, after having a fight with his wife, takes 25 tablets of his brother's tuberculosis medication (300 mg of INH) in an attempt to commit suicide. 2 hours after taking the tablets he collapses and has seizures. What would be the line of management to control his seizures?

IV pyridoxine 1gm/gm of INH ingested

25-year-old woman presents for continuing care; she has been HIV positive for 1 year and remains asymptomatic. The patient appears healthy and denies alcohol or drug use. Her current CD4+ T-cell count is 300/mm3. What complication of pregnancy is most likely in this patient?

Infectious complications

29-year-old man presented 3 days ago with sore throat and fever; he was treated with amoxicillin and is now complaining of generalized fatigue, abdominal pain, and maculopapular rash. The patient is sexually active with a single girlfriend who was sick 1 month ago but is now better. The most likely diagnosis is

Infectious mononucleosis

A 15-year-old boy presents with severe pharyngitis; he has been experiencing malaise and fatigue for approximately 1 week. He has been sent home twice from school for reportedly falling asleep in class. Physical examination is remarkable for bilateral anterior/posterior cervical lymphadenopathy and splenomegaly. Body temperature is 39.6° C. A CBC is performed and is remarkable for a WBC of 6,800/µL with a differential of 30% neutrophils, 38% lymphocytes, 14% atypical lymphocytes (see image), and 18% monocytes. Liver function tests are ordered, and the following results are obtained: AST level of 200 U/liter, ALT level of 250 U/liter, and an alkaline phosphatase level of 188 U/liter. A chest radiograph is negative. A throat screen for group A streptococcus is negative. Based on the clinical history and laboratory test results, an additional laboratory test is ordered; this test is positive. What is the most likely diagnosis?

Infectious mononucleosis

60-year-old woman presents with pyrexia, malaise, and dry cough. 15 days ago, the patient had an upper respiratory tract infection with pyrexia. The chest shows an interstitial pattern of lymphocytic inflammatory infiltrate. What pulmonary infection is causing the patient's symptoms?

Influenza A

4-year-old boy presents with skin eruptions, fever, and diarrhea. Skin eruptions developed 1 week ago after exposure to multiple mosquito bites that left weepy crusted areas. Over the past 2 days, the boy has become quiet, sleepy, and febrile and has had a few loose stools. His past medical history is non-contributory, and his immunizations are current. On examination, you find a child in a mild distress; his temperature is 39°C. Heart rate is 100/min, and respirations are 22/min. On the skin of the arms and trunk, you notice multiple excoriations: a few fragile thin-roofed flaccid transparent bullae with a clear yellow fluid that turns cloudy and dark yellow. Several bullae are ruptured, leaving behind rims of scales around erythematous moist bases, but no crusts. You also notice patches of skin of brown-lacquered appearance, with collarettes of scale and peripheral tube-like rims. What is the primary mechanism of action of the antibiotic that would best treat this patient's most likely diagnosis?

Inhibition of peptidoglycans synthesis

50-year-old healthy and asymptomatic man has had pyuria noted on 2 urinalyses performed by his insurance company. He is married and has never had a sexually transmitted disease (STD). He has never had tuberculosis, doesn't work or volunteer, or live in a group home or institution. 3 weeks ago, you treated him with amoxicillin/clavulinic acid for conjunctivitis complicated by periorbital cellulitis. His physical exam, including his prostate exam, is normal. His diagnostic studies include: Urinalysis no protein, blood, glucose, casts. 15 white cells/mm3 Urine culture no bacterial growth Urethral culture for STD normal Chest X Ray normal Tuberculin test normal Urine Tuberculin Culture pending Serum Creatinine 1.3 mg/dl Which is the most likely cause of his pyuria?

Interstitial nephritis

63-year-old diabetic woman is seen by her primary care physician. Despite having been an insulin dependent diabetic for over 20 years, her blood sugars remain poorly controlled. No amount of counselling seems to have made a difference to her attitude. At this visit, she complains of left-sided ear pain. She noticed it the previous night; she was unable to sleep with her head resting on the affected side. Since then, the pain has rapidly increased, and she feels feverish. The photograph shows the affected area at the time of the visit. What is the next step in treatment of her condition?

Intravenous ceftazidime

30-year-old male immigrant worker presented 4 weeks ago with a chronic cough, blood-stained sputum, and night sweats. His PPD was 15 mm and pulmonary tuberculosis was diagnosed. Treatment was started at that time. Today, he is back for a checkup with the presenting problem of "pins and needles" sensation in his hands. What drug is most likely causing this type of adverse effect?

Isoniazid

42-year-old woman presents with acute onset of high fevers, cough, photophobia, and bradycardia. Physical examination reveals normal vital signs, temperature of 38°C, conjunctival suffusion, and petechiae. The patient describes camping in the Grand Canyon. Microscopic examination of Giemsa-stained thick blood smears shows numerous spirochetes; a diagnosis of tick-borne relapsing fever is made. Treatment is initiated with penicillin, and 2 hours later, the patient's condition deteriorates. Her temperature increases to 39.5°C with severe rigors, myalgias, leukopenia, and hypotension. Within 24 hours, the patient has defervesced, and deterioration is reversed. What is the most likely cause of the patient's response to treatment?

Jarisch-Herxheimer reaction

34-year-old man has a rapidly developing cough, dyspnea and expectoration with blood-tinged sputum. On examination, the patient is toxic, febrile, and rhonchi are present. The patient has hyponatremia and proteinuria; a chest X-ray shows consolidation in the right hemithorax. What is the most likely diagnosis?

Legionella pneumonia

55-year-old man presents with a 3-day history of anorexia, fatigue, malaise, non-productive cough, shaking chills, and watery diarrhea. Temperature is 103 F. Blood pressure is 142/86 mm Hg, pulse is 90 bpm, and respirations are 20. Chest X-ray shows small infiltrates. Induced sputum samples do not reveal any predominant bacteria. What is the most likely diagnosis?

Legionnaire's disease

45-year-old man presents with a 3-day history of fever (maximum temperature of 103.5° F), chills, anorexia, diarrhea, and a non-productive cough. On general examination, pulse is 98/min, RR is 24/min, BP is 120/60 mm Hg, and temperature is 103.5° F. There are coarse basal crepitations and scattered rhonchi on examination of the lungs. Exam of other systems is normal. Chest X-ray (CXR) shows patchy alveolar infiltrates with consolidation in the lower lobe. Complete blood count reveals leukocytosis; sputum Gram stain reveals only a few polymorphonuclear (PMN) leukocytes, and no predominant pathogens. What is the most likely diagnosis?

Legionnaires' disease

55-year-old male who had suppurative pneumonia becomes increasingly toxic. He becomes increasingly dyspneic and hypoxemic. He becomes progressively difficult to oxygenate despite increasing the PEEP and the oxygen supply to 100%. The patient remains afebrile. The patient thus shows classical adult respiratory distress syndrome. He dies after 3 weeks despite all measures. During autopsy the lungs of this patient would be

Liver-like

The mother of a 6-week-old male infant presents because the infant has been running a high fever; he appears ill and is constantly crying. After further investigation, you diagnose the infant with bacterial meningitis. You begin treatment with an aminoglycoside while waiting for the results of the labs you ordered. You remember in a prior discussion with the pediatrician that you need to add ampicillin to the treatment. Ampicillin is used empirically for the possible presence of what infection in this patient?

Listeria monocytogenes

40-year-old man has been working 16 hours a day producing a documentary for television. He has a productive cough with yellow sputum production that has been increasing for several days. He has a fever, and the Gram stain of the sputum shows 4+ Gram-positive cocci in chains. What is the most likely diagnosis?

Lobar pneumonia

55-year-old man presents with shortness of breath and a productive cough with yellow phlegm for 2 days; he has had blood-tinged sputum for the last 3 hours. He has smoked 2 packs of cigarettes for the past 35 years. He has a temperature of 102°, and rhonchi, wheeze, and crepitations are heard over the right hemithorax. A chest X-ray shows a dense lobar infiltrate in the right hemithorax. What is the most likely diagnosis?

Lobar pneumonia

75-year-old man presents to his pain management office for follow-up after a lumbar laminectomy 2 weeks ago. He states that he has had a fever for the past 6 days. He denies any headache, chest pain, shortness of breath, cough, abdominal pain, nausea, diarrhea, vomiting, or extremity pain. He has a past medical history of hypertension, hyperlipidemia, chronic lumbar stenosis (now status post laminectomy), and type 2 diabetes mellitus. He also has a history of intravenous drug use. He was referred for an MRI of the spine, which revealed destruction of the vertebral body of L4 with significant collapse. What is the most likely additional clinical manifestation in this patient?

Lower back pain

32-year-old woman returns from a 2-week camping trip along the Appalachian Trail in New York; she presents with a low-grade fever and a non-pruritic rash on her back and buttocks. Physical exam reveals 2 large 5 cm erythematous lesions, with central clearing on her low back and buttocks. There is no lymphadenopathy. CBC with differential and ESR are normal. What is the most likely diagnosis?

Lyme disease

30-year-old woman presents with a 1-week history of a painless sore on her genitals. On examination, a solitary non-indurated ulcer on her labia is noted; there is a nonvascular base, and it is associated with tender, unilateral, inguinal and femoral lymphadenopathy. What is the most likely diagnosis?

Lymphogranuloma venereum

17-year-old boy was diagnosed as HIV-positive 4 months ago. He has had little access to medical care for most of his life and has been homeless for the past year. You discover that he has no reliable evidence of routine child vaccinations. His CD4+ T-cell count is 100/mm3. Which vaccine would be contraindicated in this patient?

MMR

70-year-old man with hypertension, diabetes, obesity, and coronary artery disease presents with a 3-day history of fever, headache, nausea, vomiting, lethargy, and myalgias. His wife states that the symptoms began the day after a summer evening walk around a lake. Today, his condition has worsened; he has developed a diminished level of consciousness, behavioral changes, and abnormal movements. His physical exam reveals a lethargic man with photophobia, cranial nerve deficiencies, neck stiffness, and abnormal extremity movements. Based on your suspected diagnosis, what is the next step in the management of this patient?

MRI of the brain

22-year-old woman presents with an 8-hour history of headache and vomiting. She resides in a college dormitory; she has no remarkable travel history, and reports eating food from a street vendor 24 hours before becoming ill. The patient is lethargic and disoriented. On examination, she is found to have a temperature of 38.5° C and a petechial rash on her legs. Gram stain of exudate from a skin lesion shows Gram-negative diplococci. A lumbar puncture is performed; the cerebral spinal fluid (CSF) reveals a leukocyte count of 5/μL consisting of primarily neutrophils. A Gram stain of CSF is negative for bacteria. What is the most likely diagnosis?

Meningococcemia

31-year-old female nurse who works at a local hospital presents with a purpuric rash covering her arms, legs, and abdomen, as well as fever, chills, nausea, abdominal tenderness, tachycardia, and generalized myalgias. Prior to the development of the rash, the patient noted that she had a headache, cough, and sore throat. Laboratory studies were positive for gram-negative diplococci in the blood, along with thrombocytopenia and an elevation in PMNs. Urinalysis showed blood, protein, and casts. Vital signs are as follows: BP 92/66, P 96, RR 14, T 39. The patient denies any foreign travel and does not have any sick contacts. She is admitted to the hospital and placed in respiratory isolation. What is the most likely diagnosis?

Meningococcemia

34-year-old woman, an immigrant from South America, presents with an acute onset of chest palpitations and shortness of breath. The patient also gives a 1-week history of fever, fatigue, and weakness. Echocardiography reveals that her heart is dramatically increased in size. Electrocardiogram (EKG) shows low voltage QRS with atrioventricular (AV) conduction abnormality. It is determined that she has Chagas disease. What is a complication that occurs during the acute phase of this patient's condition?

Meningoencephalitis

38-year-old asymptomatic woman with a 30-year history of diabetes has a yearly urinalysis and spot urine albumin to creatinine ratio as part of her yearly laboratories. How do you interpret her urinary findings? Blood, glucose no blood or glucose Protein Trace Spot albumin/creatinine ratio 40 mg/g Cells 10 white cells/mm3, no red cells Casts None Nitrite, Leukocyte esterase positive nitrite and positive leukocyte esterase Bacterial growth 50 colony forming units

Microalbuminuria

55-year-old man is hospitalized with COPD; 2 days admission, he develops a fever of 40°C. He has an increased respiratory rate of 25/min, a productive cough, and left-sided pleuritic chest pain. Chest auscultation reveals localized signs of consolidation. Chest radiographs are ordered and are significant for the presence of diffuse peri-bronchial interstitial infiltrates and dense alveolar consolidation. A sputum specimen is acquired for culture and Gram stain. The Gram stain is significant for the presence of large numbers of white blood cells and Gram-negative diplococci. Some of the white cells contain ingested Gram-negative diplococci. The culture is positive for 4+ gray colonies with the following characteristics. Refer to the table. CULTURE TEST Result Growth on blood agar Pos Growth on chocolate agar Pos Growth on MacConkey agar Neg Oxidase Pos Gram stain Gram-negative diplococci (kidney bean shaped) Glucose Neg Sucrose Pos Maltose Neg ONPG Neg Beta lactamase Pos H2s Pos This patient has acquired pneumonia, based on the clinical presentation/history and microbiology results, due to what?

Moraxella catarrhalis

5-year-old child was brought to the outpatient clinic because of some vesicles that appeared on his face .The mother said that her child's friend has a similar lesion. The vesicles are pearly white umblicated, not surrounded by erythema, and not associated with itching. The mother is concerned that it may be something contagious. What is the most likely diagnosis?

Molluscum contagiosum

29-year-old man presented 3 days ago with a sore throat and fever; he was treated with amoxicillin and now presents with generalized fatigue, abdominal pain, and a maculopapular rash. The patient is sexually active with one partner who was sick 1 month ago; she is now better. What is the most important single test to be done now?

Monospot heterophile antibody test

4-year-old boy presents with skin eruptions, fever, and diarrhea. Skin eruptions developed 1 week ago; he was in the Caribbean with his parents, and he was exposed to multiple mosquito bites. It was at the sites of mosquito bites that his parents initially noticed weepy, honey-colored crusted areas; the boy notes itching. Over the past 2 days, he has become quiet, sleepy, and febrile; he has had a few loose stools. His past medical history is non-contributory, and his immunizations are up to date. On examination, you find a child in a mild distress; his temperature is 39°C. Heart rate is 100/min, and respirations are 22/min. On the skin of the arms and trunk, you notice multiple excoriations, vesicles, and 'collarette' of scale surrounding the blister roof at the periphery of ruptured lesions; also seen are bullae, with erythematous bases between and adjacent to the lesions. What topical medication should you prescribe in addition to oral medications?

Mupirocin

43-year-old man presents in acute respiratory distress. He is a known HIV patient who has progressed to a full-blown AIDS infection. He has recently been undergoing chemotherapy, but the treatment has had no effect on the increased viral load level. He has a 2-week history of night sweats, severe fatigue, chills, and fever. His physical examination is remarkable for an enlarged liver (as detected by palpation) 5 cm below the costal margin. The patient has an elevated body temperature of 40° C. He has a decreased WBC count of 3,000/uL and a decreased Hgb of 6.8 g/dL. Electrolytes, chemistries, and urinalysis are normal. Blood and stool are obtained for mycobacterial cultures. After 20 days, the culture is positive for a mycobacterial species that grows in smooth, nonpigmented colonies. What is the most likely causative agent?

Mycobacterium avium-intracellulare

28-year-old HIV-positive man presents with night sweats and chronic cough with very little sputum. His sputum for acid-fast rods is positive. His PPD skin test is negative. His CD4 count is 120/mm3. His sputum specimen is sent for culture, and his treatment is started. What organism is likely to be isolated from this patient's sputum?

Mycobacterium avium-intracellulare complex

40-year-old man presents with chest pain. The patient has a history of chronic obstructive pulmonary disease (COPD). He has been a smoker for the past 30 years. He has a 2-week history of mild fatigue and a chronic non-productive cough. He is afebrile, alert, and has normal vital signs. A chest radiograph is ordered, and it is found to be significant for bilateral interstitial infiltrates. A complete blood count (CBC) is significant for a slightly elevated white blood count. The erythrocyte sedimentation rate is elevated. Sputum is obtained for bacterial, fungal, and mycobacterial cultures. Both bacterial and fungal smear preparations are negative, as are subsequent culture results. Mycobacterial specimen acid-fast stains are positive for acid-fast organisms. The patient is placed in an isolation room pending the culture identification of the organism. The organism is found to exhibit photochromogenicity, and it produces yellow pigment. On day 12, there is growth of mycobacteria that produces the following laboratory identification test results: GROWTH RATE NIACIN NITRATE REDUCTION OPTIMUM TEMPERATURE TWEEN HYDROLYSIS UREASE 12 DAYS NEG POS 37°C POS POS What organism is causing the pulmonary infection in this individual?

Mycobacterium kansasii

30-year-old man presents with a 15-day history of fever and worsening dry cough, headache, and scratchy sore throat. The general appearance is non-toxic. On examination, he has a erythematous tympanic membrane, mild pharyngeal erythema with no exudates, and no cervical lymphadenopathy. Chest auscultation reveals rhonchi and rales scattered over the chest wall. A chest X-ray shows plate-like atelectasis and nodular infiltrate. What is the most likely diagnosis?

Mycoplasma pneumoniae

7-year-old girl with varicella is brought to the emergency room by her parents; they explain that the child is experiencing pain in her leg. Examination reveals a low-grade fever of 38.5° C and mild chickenpox (<100 lesions, most of which are crusted). The child has tachycardia and severe pain in her left thigh. There is a single lesion on the outer thigh it is surrounded by mild erythema and anesthesia, but no swelling. The child is highly distressed. For what potentially life-threatening condition is this child at risk?

Necrotizing fasciitis

20-year-old marine in boot camp develops meningitis. The patient had developed pharyngitis before he developed the meningitis. Which of the following organisms is responsible for the cause?

Neisseria meningitidis

50-year-old man presents for the evaluation of a 1-year history of progressive cognitive, motor, and behavioral problems. He complains of inattention, reduced concentration, slowing of processing, and difficulty changing mental sets. What started as slow movements now is clumsiness and problems with coordination. His friend states that the patient is "not himself anymore" and has become apathetic, non-communicative, and "down." He is HIV-positive and was diagnosed with AIDS 2 years ago because of the presence of Pneumocystis carinii with CD4 of 100. He had an excellent response to antiretroviral therapy, however, and his last CD4+ lymphocyte counts were normal and viral load undetectable. On examination, you find an apathetic male in mild distress. Neurological exam shows loss of coordination, unsteadiness, generalized weakness (more pronounced in legs), ataxia, and tremor. What should be the next diagnostic step in this patient?

Neuroimaging methods

55-year-old male firefighter suddenly develops fever, palpitations, and shortness of breath 7 days after skin transplant for severe facial burns. He also has fever resistant to intravenous antibiotics therapy introduced at the onset of fever. Because of oropharyngeal lesions, he is on parenteral nutrition. On examination, transplant shows neither signs of infections nor signs of rejection. Patient appears lethargic, with a blood pressure of 80/40, pulse rate of 120, respiratory rate of 18, and temperature of 103.4°F. Stat CBC shows neutropenia and eosinophilia. Why would you order a blood culture for systemic fungal infection?

Neutropenia

43-year-old man visits the internal medicine clinic of a university hospital presenting with a 3-week history of shortness of breath, fever, and chills. Examination shows a temperature of 38.0°C. Laboratory results suggest hypoxemia with PO2 of 74. Previous history shows the patient has been HIV-1 positive for 4 years and presently has a CD4+ T-cell count of 50/mm3. A presumptive diagnosis of Pneumocystis carinii pneumonia (PCP) is made, which is confirmed by bronchoalveolar lavage. What would be expected from chest auscultation in this patient?

No findings

31-year-old man presents with a tick bite. He describes locating a tick in the left axillary area while showering in the evening, and he denies that the tick was present the previous evening. He removed the tick with forceps and cleaned the wound with alcohol. Examination of the bite shows local erythema and mild induration 3-5 mm diameter. The tick is identified as an adult female Ixodes scapularis. What is the recommended course of management for this patient?

No treatment needed

45-year-old man came to the clinic complaining of a sudden blurring of vision that started a week ago. On examination, he was found to have a vision of 10/20 in the right and 20/20 in the left. His right eye also showed defective color vision, and he describes colors as washed out. He has never previously had problems in his eyes. He works in an assisted living house for elderly, and he was PPD converted to positive 4 months ago. He was started on Ethambutol, INH,and Rifampicin as recommended by his physician. What is the most likely diagnosis?

Optic neuropathy

17-year-old female high school student presents with copious yellow vaginal discharge. She has been sexually active with a new partner for the past several months. She states that they use condoms because she intends to go to college and does not want to become pregnant. However, there have been a few occasions in the beginning of the relationship where they did not use protection. She has no history of STIs (Sexually Transmitted Infections). This is her first sexual partner, but she is unsure if her partner is monogamous. A speculum examination reveals a "strawberry" cervix, petechial lesions in the upper vagina, and a malodorous, yellow-green discharge. A potassium hydroxide preparation reveals no organisms, and results of a Giemsa stain are shown. What is the most appropriate treatment?

Oral metronidazole and test the patient and her partner for other STIs

89-year-old Caucasian man is brought in by his daughter due to pain in his left shin. He bumped his leg on a coffee table about 3 weeks ago; he developed some mild discomfort, bruising, and a small gash in the skin. It seemed as if he was healing well, but his condition has worsened over the past few days. Now he is moaning due to pain, and he says it hurts to walk on the leg. He describes the pain as "horrible" and an 8/10. The daughter reports the pain keeps him up at night and is unresponsive to ibuprofen and narcotic pain pills. He denies fever and chills. On physical exam, the patient is in obvious pain and is assisted to the exam table with limited weight bearing on his left leg. The lower extremities are examined; significant findings include healing and a scabbed lesion of approximately 3 cm in length across mid-tibia, with surrounding erythema and edema. Tenderness is elicited along the shin, extending well past the area of erythema. Homan's sign is negative. Distal pulses, temperature, coloration, knee range of motion, and lower extremity reflexes are symmetric and normal. Right lower extremity is normal. What is the most likely diagnosis?

Osteomyelitis

14-year-old boy goes to the school nurse with a swollen hand and painful arm. He reports that he was bitten on the hand by a cat the previous evening. The nurse notes an abscess formation at the wound site, a temperature of 38.5° C, axillary tenderness, and erythema along the dorsal forearm. Following referral to the patient's family practice, laboratory results show a leukocyte count of 15,000/μl and numerous immature neutrophils. Gram stain of exudate from the abscess reveals Gram-negative coccobacilli. Wound cultures yield a Gram-negative rod that grows rapidly on blood and chocolate agar. What organism is the most likely cause of the infection?

Pasteurella multocida

5-year-old boy presents with a facial skin lesion that started as a reddish itching pimple on the cheek; it spread over the last 2 days and now it involves the whole cheek. The child was previously healthy; he does not have any known allergies, and his immunizations are up to date. On examination, the child does not appear in any distress. On his right cheek there is a shiny, fiery-red and tense infiltration approximately 6 x 6 cm in diameter, with irregular periphery and well-marginated, slightly elevated borders. The lesion is tender and warm. Right preauricular lymph nodes are enlarged, firm, and tender. The rest of examination is normal. What should your pharmacological approach be?

Penicillin

Mrs. Sanchez is a 38-year-old female who is G 5 p 4. Her children have been passing around a nasty case of impetigo. She presents with patches of pinhead-sized vesicles with some covered by a yellow crust. Her case of impetigo needs to be treated, but with her pregnancy at 18 weeks many drugs are off limits. Which drug can be used to treat a pregnant woman?

Penicillin

18-year-old man presents with a 2-day history of fever and sore throat. He has no known drug allergies. On physical exam, his temperature is 102°F, HR is 92/min, BP is 110/76 mm Hg, and RR is 22/min. His rapid antigen detection test is positive for group A Streptococcus. What drug is the first-line therapeutic agent for the treatment of this patient's condition?

Penicillin V

12-year-old Caucasian girl presents with a sore throat. The onset of symptoms was about 24 hours ago. The patient experiences pain in her throat, especially with talking or swallowing. She is fatigued because throat pain prevented her from sleeping last night. Throat lozenges have not been helpful. Several classmates have been out sick recently. She denies nasal congestion, rhinorrhea, and cough and is unsure of fevers. This patient has no chronic medical conditions, takes no medications, and has no known drug allergies. On physical exam, she appears slightly ill and fatigued. HEENT exam is positive for bilateral cervical lymphadenopathy and inflamed posterior oropharynx without exudate. She does have normal range of motion of the neck without eliciting pain. Her heart, lung, and abdominal exams are normal. No other lymph nodes are palpable. Weight 92 lb, height 4'8", pulse 95, BP 102/60, temperature 99.2°F/37.3°C. What is the most appropriate next step in the care of this patient?

Perform rapid antigen testing for group A streptococcus.

55-year-old male becomes febrile and dies at home. The patient was unable to care for himself and was mainly bedridden except for short periods when he was placed in the wheelchair and taken out in the open. The probable cause of death in this patient would be

Pneumococcal pneumonia

A 33-year-old man presents with shortness of breath. The symptoms started a week ago and have gradually worsened; he has had a low-grade fever and dry cough. He has not been exposed to anyone with a respiratory tract infection. Past medical history is significant for being HIV positive; he was first diagnosed 4 years ago. He has had several opportunistic infections, and reports that his CD4 count was 220/mm3 a few months ago. He has never been hospitalized or had any surgery. Current medications include 2 nucleoside analogues and a protease inhibitor, a regimen that he was placed on a month ago after his viral load was found to be 400,000 copies/mL. Family history is negative for diabetes, hypertension, or cancer. Social history reveals that he is homosexual with multiple partners. He does not smoke or use illicit substances. Review of systems is negative for change in appetite, weight loss, chest pain, abdominal discomfort, diarrhea, dysuria, or urethral discharge. On examination, the patient is thin, awake, alert, and interactive. Temperature is 100.0°F, blood pressure is 100/70 mmHg, pulse 88 bpm, and respirations 20/min. Tympanic membranes are pearly gray with positive light reflexes bilaterally. The oropharynx is slightly red, but there is no exudate. There is mild prominence of the cervical lymph chains bilaterally. Lungs reveal coarse rhonchi to auscultation bilaterally, but no focal rales or wheezes. Extremities are thin, but fully developed. Neurological testing is grossly nonfocal. Pupils are equal and reactive; muscular strength is full and symmetric. Gait is steady, and deep tendon reflexes are normal. A chest X-ray is obtained, and it shows diffuse bilateral infiltrates that have a ground glass appearance. There is no effusion. Cardiac silhouette is normal in width. There is no pneumothorax. Pulse oximetry shows 92% saturation on 2 liters nasal cannula. An arterial blood gas reveals PO2 of 65, as well as a slight respiratory acidosis. A complete blood count is requested. The results are as follows: White blood count 1800 cells/mm3 Hemoglobin 11.4 mg/dL Hematocrit 32.8 % Platelets 1.14 lacs/microliter CD4 count 170/mm3 With what pathogen is this patient most likely infected?

Pneumocystis carinii

30-year-old man presents with a non-productive cough with fever and dyspnea. A chest radiograph reveals bilateral perihilar infiltrates. The patient has been HIV-positive for the last 5 years. What is the most likely diagnosis?

Pneumocystis carinii pneumonia

32-year-old HIV-positive man presents with a 1-week history of shortness of breath and a nonproductive cough. On physical exam, he is tachycardic, tachypneic, and febrile. He has lost weight without a change in dietary habits. Auscultation of his chest reveals bibasilar crackles. A chest X-ray is ordered and demonstrates diffuse interstitial infiltrates that are perihilar and symmetric. An arterial blood gas shows moderate hypoxemia. What is the most likely diagnosis?

Pneumocystis jiroveci

35-year-old man is admitted to the hospital with progressive shortness of breath, fever, and worsening cough. He began losing weight 2 months ago, associated with anorexia, intermittent diarrhea, night sweats, and non-productive cough. He lost >20 lb by admission. PMH unremarkable. He admits excessive alcohol consumption on weekends but denies tobacco and IV drug use. He mentions a previous homosexual encounter. Chest is normal to percussion and clear by auscultation except for some scattered rhonchi. Heart is normal except for tachycardia. Abdomen is soft with normal bowel sounds. Genitalia normal, but there is a painful 2 cm ulceration at the anal verge. Neurologic exam unremarkable. Chest radiological findings show diffuse bilateral interstitial infiltrates. Arterial blood gases on room air show pO2 57 mm Hg, pCO2 31 mm Hg, pH 7.45. Alveolar-arterial O2 gradient is 55 mm Hg. Bronchoalveolar lavage fluid with lung biopsy shows presence of cysts. Sputum cytology is negative for acid-fast bacilli. What is the most likely diagnosis?

Pneumocystis pneumonia

30-year-old immunocompromised patient presents with a 2-week history of breathlessness and a non-productive dry cough. The patient is afebrile, pulse is 100, and BP is 110/70 mm Hg. On auscultation, scattered rales all over the chest are heard. A chest x-ray shows diffuse air-space and interstitial shadowing in both lungs. What is the most likely diagnosis?

Pneumocystis pneumoniae

27-year-old woman presents because she noticed some cobblestone changes in her genital area 1 month prior. She has no other symptoms. Her current sex partner has similar changes on the skin at the base of his penis. Examination of the genitalia reveals multiple dry small skin-colored, papular keratotic lesions in the skin of the perineal area. The rest of the examination is normal. You suspect the diagnosis of condyloma acuminata. Which of the following is an appropriate next step in therapy?

Podofilox 0.5% gel

52-year-old woman, with a body mass index of 35, presents for evaluation of back pain that has been present for several months. The pain becomes worse at night and is accompanied by stiffness. For the past week, she has been experiencing night sweats and fever. She relates that she had a positive PPD test a year ago and did not follow up as directed. An X-ray of her lumbar spine reveals osteopenia, lytic and sclerotic lesions, and cortical breakdown of vertebral bodies L4 and L5. What is the most likely diagnosis?

Pott Disease

12-year-old boy is investigated for difficulty with breathing; the difficulty has occured for several weeks. A chest X-ray reveals subpleural nodule in the right lung midfield as well as enlarged mediastinal lymph nodes. What is the most likely diagnosis?

Primary tuberculosis

6-year-old boy develops a low-grade fever with no other symptoms. A chest X-ray shows a peripheral solitary mid-lung nodule and marked hilar lymphadenopathy. Of what are these findings suggestive?

Primary tuberculosis

24-year-old woman has had 5 urinary tract infections in the past year. All infections have occurred after sexual intercourse. She uses oral contraceptives, but no spermicides, diaphragms, or condoms. How can she best prevent further recurrent urinary infections?

Prophylactic antibiotics

10-year-old boy presents with chronic otitis media with accompanying purulent discharge occurring over the past 6 months. He is very irritable, and his mother has been increasingly frustrated that he has not completely responded to the treatments. Which of the following organisms is most likely associated with this patient's condition?

Pseudomonas aeruginosa

10-year-old Caucasian boy presents with fever and a severe throbbing pain and swelling in the right sole since morning. He accidentally stepped on a nail while playing in the backyard 1 week previously. Since he was wearing rubber-soled shoes, his father assumed that the wound would not be deep; he dressed the wound at home. The pain, redness, and swelling at the wound have increased over the last few hours. Vitals are as follows: temp 101° F; PR 92/min; BP 120/80 mm Hg; and RR 19/min. Systemic exam is unremarkable. Examination of the right sole reveals a 2 x 2 cm wound with drainage of pus over the 2nd metatarsal; there is surrounding edema and redness. There is extreme tenderness and limitation of movement of the entire right foot. CBC, ESR, X-ray of the right foot, and culture of secretions from the wound are ordered. X-ray reveals soft tissue swelling over the 2nd metatarsal. Osteomyelitis is suspected. What is the most likely causative organism?

Pseudomonas aeuroginosa

A female patient presents with a 3-week history of weight loss, fever, productive cough, draining sinuses, night sweats, shortness of breath, difficulty breathing, and chest pain. She reports being treated for a tooth abscess 2 weeks prior to the symptoms. Past treatment includes acetaminophen, fluids, and rest. While in the office, she displays difficulty breathing, moist and clammy skin, and a mild increase in temperature. The chest radiograph displays pleural effusion. What is the most likely diagnosis?

Pulmonary actinomycosis

An infant has several episodes of pneumonia. A radiograph reveals a localized area of consolidation near the base of the right lung. Angiography reveals that segment of the lung receives blood supply from the systemic arteries and not the pulmonary arteries. What is the most probable diagnosis of this consolidated mass?

Pulmonary sequestration

36-year-old woman presents with malaise, headache, sore throat, and unusual fatigue. She has a history of intravenous drug use and has been diagnosed with AIDS. Examination reveals a temperature of 40° C, a maculopapular rash, and lymphadenopathy. Laboratory findings confirm the diagnosis of toxoplasmosis. What is (are) the drug(s) of choice in the initial treatment of CNS toxoplasmosis in AIDS patients?

Pyrimethamine and sulfadiazine

29-year-old man presents with unilateral swelling of the knee and a 1-month history of urethral discharge. Physical examination is unremarkable with the exception of marked swelling of the left knee. Urethral swabs show pus and culture are negative for Neisseria gonorrhoeae, chlamydia, and Mycoplasma. What is the most likely diagnosis?

Reiter's syndrome

40-year-old HIV patient presents for a routine physical exam; he has a 1-week history of fatigue and a non-productive cough. Chest radiographs are positive for cavitary-like lesions. He has a fever of 38°C, respiration rate of 25/min, and a decreased WBC count of 2,500/µL with a left shift. A bronchoscopy and cultures for fungus, mycobacteria, and bacteria are ordered; blood cultures are also ordered. The KOH preparation is negative for fungal elements. The AFB stain is negative for acid-fast organisms. The bacterial Gram stain is significant for few WBCs, no epithelial cells, and a moderate numbers of Gram-positive, cocco-like bacilli with occasional branching. Bacterial cultures are positive for 4+ dark pink colonies that are Gram-positive rods, non-motile, H2S-negative, non-beta-hemolytic, catalase-positive, and esculin-negative. The blood cultures eventually grew out the same organism. What is the most likely organism isolated causing disease in this patient?

Rhodococcus equi

18-month-old infant presents with a 5-day history of fever of 104°F. On physical examination, you note a mildly irritable infant who has not been feeding well. There are no other clinically significant findings. You prescribe acetaminophen (Children's Tylenol) and tell the mother to monitor the infant's fever for the next few days; if the fever goes down, everything should be fine. The mother calls the next day and says that the fever has stopped, but a rash has developed, and she is concerned. The infant examination reveals a diffuse fine maculopapular rash. Presently, the child does not appear ill. What is the most likely diagnosis?

Roseola

A previously healthy 27-year-old woman presents with rash and malaise. Examination reveals normal vital signs, as well as multiple lesions on the palms of her hands, the soles of her feet, and on her trunk. Lesions are nonpruritic, erythematous papules that are hyperpigmented with tightly adherent scales. Infrequent annular plaques are seen on the mouth and nose. The patient describes a history of painful oral lesions, fever, headache, and pharyngitis; medical history is unremarkable. What is the most likely diagnosis?

Secondary syphilis

45-year-old man presents with a fever accompanied by a productive cough. He has had the symptoms for several weeks. His temperature rises in the evenings, and he has experienced weight loss. The chest X-ray shows upper lobe cavitary lesions. What is the most likely diagnosis?

Secondary tuberculosis

A sexually active woman with multiple partners presents with a 2-day history of red swollen left knee. On examination there is tenderness and decreased range of motion. There is no history of trauma, no affectation of other joints, and she has inflamed right achillis tendon. The most likely diagnosis is:

Septic arthritis

32-year-old man presents with fever and blurred vision in his left eye. Medical and social history show that the patient is homeless, uses drugs intravenously, and has been HIV-1 positive for 1 year, with a recent CD4+ T cell count of 80/mm3. The patient has tachycardia, hypotension, and a temperature of 38.5° C. Funduscopy reveals a white perimacular lesion, and numerous white plaques are detected in the pharynx. A diagnosis of disseminated candidiasis is made and the is patient given 1 g/kg intravenous amphotericin B. Owing to the toxicity of this antifungal drug, what should be monitored closely in this patient?

Serum creatinine

25-year-old man presents with a painless, ulcerated lesion on the glans of his penis. He admits he had unprotected sexual intercourse with a sex worker 3 days ago. Since that time, he has not had sexual intercourse. Other than his wife, he denies having had other sex partners in the last 12 months. Past medical history and family history are unremarkable. The patient has normal vital signs. Physical examination reveals an indurated, painless, non-secreting chancre at the tip of his penis. There is no urethral discharge. Enlarged, painless lymph nodes are palpated on both inguinal regions. The remainder of the examination is within normal limits. What is the best next step in management?

Single IM dose of penicillin G benzathine

29-year-old man presented 3 days ago with sore throat and fever; he was treated with amoxicillin and is now complaining of generalized fatigue, abdominal pain, and maculopapular rash. The patient is sexually active with a single girlfriend who was sick 1 month ago but is now better. Most serious short term complication of the disease is

Spleen rupture

52-year-old chronic alcoholic dies due to some unknown cause. At autopsy, both the lungs are filled with hundreds of 1 - 3 mm firm, rounded, tan nodules. What infectious agent is most likely to produce this grossly apparent pattern?

Spleen rupture

15-year-old boy presents with a 1-week history of malaise, a low-grade fever, and a sore throat. On exam, you note pharyngeal erythema, scant yellow exudates, and enlarged posterior cervical lymph nodes. There are no current signs of airway compromise. There is no skin eruption noted, and the rapid strep screen is negative. What other physical examination finding is usually present with this condition?

Splenomegaly

26-year-old woman employed as a landscape gardener and part-time pet groomer presents with a sore on her arm. Examination shows a firm, localized, and painless subcutaneous nodule that has recently ulcerated. Gram stain of exudate from the ulcer shows pus and yeast. When exudate is cultured at 25° C, it grows a white fluffy colony with rosette conidia seen microscopically. What is the most likely etiology of the nodule?

Sporothrix schenckii

27-year-old woman presents with fever, sore throat, myalgia, and watery diarrhea. She also has a rash. She describes it as starting on her trunk, then spreading to the limbs, including palms and soles. On examination, the patient is hypotensive and has decreased level of consciousness. Her menses started 4 days ago and is still on. The tongue is red as a strawberry. What is the most likely diagnosis?

Staphylococcal toxic shock syndrome

A 27-year-old man eats a meal consisting of ham casserole with potatoes and green beans. 3 hours later, he abruptly begins vomiting; he experiences profuse watery diarrhea, abdominal cramping, and headache. Examination determines that he is diaphoretic and salivating; he has normal vital signs. The patient is encouraged to rest and take copious fluids. The following evening his symptoms subside, and he is able to return to routine activities within 24 hours of becoming ill. This food-borne illness is most likely to be caused by what organism?

Staphylococcus aureus

43-year-old man without any significant PMHx presents with acute onset of a productive cough, shortness of breath, pleuritic chest pain, and fever. His sputum is described as "thick, brown-colored, and mucoid" but without blood. He also notes associated fatigue and night sweats. He denies chills, changes in weight, a history of travel, sick or confined contacts, exposure to animals, cigarette smoking, otalgia, sore throat, swollen glands, abdominal pain, diarrhea, rashes, myalgias, and arthralgias. His physical exam is remarkable for fever, tachycardia, and tachypnea. The lung exam is noteworthy for right lower lung field increased tactile fremitus, dullness to percussion, inspiratory crackles, and bronchial breath sounds. What is the most likely etiologic agent responsible for this patient's presentation?

Streptococcus pneumoniae

4-year-old boy presents with bloody stool and vomiting after 4 days of diarrhea, nausea, and low fever. Over the past week, several children from the neighborhood also suffered diarrhea after drinking water from the neighborhood well. The rest of his personal history is non-contributory. On examination, he looks pale, fussy and lethargic, but he appears non-toxic. His temperature is 37.8, and pulse is 135; respirations are 30, and blood pressure is 96/45. Oxygen saturation is 100. His height is 89 cm, and his weight is 10 kg; BMI is 15.6 (49th percentile for his age). His abdomen is flat, soft, and non-tender, with the liver edge palpable 3cm below the RCM; the rest of the examination is normal. Coagulation studies are normal. Coombs test is negative, and the rest of laboratory findings are bellow: Test Results Range Units Red Cell Count 3.5 3.90 - 5.50 millions/mm3 Hematocrit 27 31 - 41 % Hemoglobin 8 11.3 - 14.1 gm/dL White Cell Count 16,000 5500 - 15500 mm3 Segmental 54 32 - 54 % Lymphocytes 30 28 - 48 % Bands 10 0 - 11 % Eosinophils 4 0 - 3 % Basophils 2 0 - 1 % Platelets 75 250 - 450 x103/µL Glucose 145 100 - 200 mg/dL Creatinine 1.3 0.3 - 0.7 mg/dL Uric Acid 7.5 2.0 - 6.5 mg/dL Sodium 133 130 - 140 mEq/L Potassium 5.9 3.5 - 5.0 mEq/L Chloride 96 102 - 112 Mmol/L Calcium (Total) 7.8 8.8 - 10.6 mg/dL Bicarbonate 16 18 - 25 Mmol/L Phosphorus 6.3 3.2 - 6.3 mg/dL LDH 150 - 360 IU/L What test will confirm your diagnosis?

Stool culture

35-year-old man was admitted to the hospital 10 days ago for shortness of breath. He has chest X-ray showing lower lung consolidation and was diagnosed with pneumonia. He was treated with intravenous antibiotics and now his symptoms are resolving and his X-ray showed improvement but he is now complaining of abdominal cramps and diarrhea. What is the first best step in management?

Stool cytotoxin test

44-year-old man presents with an acute cough and 4-day history of right-sided chest pain upon inspiration. He indicates that he has been running a fever for the last few days. You ask if his cough is productive or nonproductive, and he indicates that it is productive with a yellow-green color to it. You inquire about any other symptoms, and he states that he has a history of shaking chills when he seemed to be running a high fever. You order a chest X-ray, which indicates right middle infiltrate. What is the most likely etiology in this case?

Streptococcus pneumoniae

A 14-year-old boy presents with painful swelling of his right index finger. He bites his nails regularly, and has had the same problem 3 times in the past. There are no other known comorbidities. The ER attending requests an orthopedic consultation in order to make a management decision. The clinical picture noted by the on-call orthopedic resident is shown. What is the next step in management?

Surgical drainage

It is late Saturday night in the ER. Paramedics have just brought in a 25-year-old Hispanic man. The paramedics relate that he was found by police about 1 hour ago, stumbling along the highway. The patient speaks broken English and a translator is not available for the next hour. He doesn't appear to be able to hear out of his right ear. When you become able to communicate with him, he tells you he has had progressive trouble with hearing and his balance is off. He also complains of tinnitus and is getting more headaches than he has ever had in the past. He passed the breath analyzer test. He denies use of alcohol, tobacco, or drugs. He has been in the United States for the past 6 months. He relates having 6 sexual partners in the past year. Before getting the results of the labs and x-rays, what would be the most likely diagnosis?

Syphilis of inner ear

23-year-old man presents with having 'passed' a worm. The man reveals a flatworm of about 2 - 3 cm in length and 1 cm in width, which he found 'crawling down his leg'. The patient is healthy and denies seizures, headaches, or abdominal pain. Physical examination is unremarkable. Leukocyte count and differential are within normal ranges. The patient has recently traveled, spending a year in Egypt and Kenya. What is the most likely organism identified by this patient?

Taenia saginata

28-year-old man presents with severe headaches. He states that they began a few weeks ago and that he has been taking over-the-counter medications with some relief. He reports that he has AIDS. You ask what the patient was doing prior to experiencing these headaches. He says that he was taking care of the neighbor's cat while they were on vacation. Concerned, you order a CT scan; it demonstrates multiple ring-enhanced lesions. What organism do you suspect?

Toxoplasma gondii

52-year-old man presents with a 4-hour history of a grossly soil-contaminated wound on his arm. He tried to clean it with some disinfectants, but it still looks dirty. Dead tissue and soil are visible on physical examination. The patient's immunization status is uncertain. What is the next step for tetanus prophylaxis following surgical debridement of the wound?

Tetanus immunoglobulin (TIG) and Tdap vaccine

36-year-old woman underwent a matched related donor stem cell transplant for underlying chronic myeloid leukemia. She was conditioned with cyclophosphamide total body irradiation and received recombinant DNA-monoclonal antibody. In the post-transplant period, there were no complications. She is currently receiving immunosuppressive therapy. What vaccine is appropriate for this patient?

Tetanus vaccine

25-year-old landscaper who lives in Rhode Island presents with a 2-week history of generalized malaise and an "unusual rash" on the right thigh. The patient reports that this rash has been widening but they deny any pruritus or pain in association with their other symptoms. In the past week, the patient has also noticed a constant headache and mild fever. Past medical history is unremarkable. The physical exam reveals vital signs within the normal limits and enlarged non-tender diffuse lymph nodes in cervical and inguinal areas, as well as an erythematous rash with central clearing. Based on the most likely diagnosis, what would you suggest as the initial line of therapy?

Tetracyclines

45-year-old man presents with significant weight loss (10 pounds in 4 months), cough with hemoptysis, and pleuritic chest pain. The chest X-ray shows ill-defined opacities in both the lungs; the opacities have a reticulonodular pattern. A transbronchial biopsy is performed, and it microscopically shows a few epithelioid cells with necrotic debris. What is the most likely diagnosis?

Tuberculosis

27-year-old woman who is 18 weeks pregnant states that her 3-year-old daughter was just diagnosed with erythema infectiosum (Fifth disease). An antibody test is ordered, and the woman is found to be seronegative. She is healthy and has no signs or symptoms of parvoviral infection. 2 weeks later, the test is repeated and the patient is IgM-positive. What is the significance of this test result with regard to the patient's fetus?

The patient should undergo serial fetal ultrasounds to monitor for signs of hydrops fetalis.

50-year-old man is brought to the emergency room for abdominal pain. After a diagnosis of cholecystitis, surgery is performed; favorable results are achieved. 3 days after surgery, the incision becomes infected, purulent discharge is noted, and the patient suddenly developed a 103°F fever, hypotension, and a rash on his palms and soles. Routine culture detects coagulase-positive gram-positive cocci. For what potentially life-threatening condition is this patient at risk?

Toxic shock syndrome

38-year-old HIV-positive man presents with fever, headache, right hemiparesis, and expressive aphasia. Recent CD4 count is 45, but he is not on any prophylactic medications. Computed tomography scan (CT) reveals multiple ring-enhancing lesions in the parietal and frontal lobes. What is the most likely cause?

Toxoplasmosis

43-year-old woman is admitted for nausea, emesis, ataxia, and dizziness. Previous medical history reveals HIV positive status for 4 years, with the most recent CD4 T-cell count of 100/mm3. Vital signs and neurologic exam are normal. An MRI shows 2 ring-enhancing lesions of the basal ganglia, each approximately 1 cm in diameter. The patient is treated with sulfadiazine plus pyrimethamine, and she is discharged following rehydration. Within 1 week, the patient's symptoms improve; a 2nd MRI 4 weeks later shows a significant reduction in the size of the lesions. What is the most likely diagnosis?

Toxoplasmosis

23-year-old woman visits a community clinic presenting with vaginal pain, itching, and odor. The patient reports that she was treated for gonorrhea 3 weeks earlier. Examination shows a white vaginal discharge. Cervical cultures are submitted for Neisseria gonorrhoeae and Chlamydia trachomatis. Gram stain reveals predominant, slender, Gram-positive rods with rare neutrophils. Wet mount of a cervical smear shows flagellate protozoa. What is the most likely cause of the presenting problem?

Trichomonas vaginalis

27-year-old man presents with burning pain with urination; there is also some urethral discharge. Several laboratory tests are done, including a Gram stain and culture on a sample of the discharge. The results are negative and gonorrhea is ruled out. He is diagnosed with nongonococcal urethritis. His doctor tells him that he suspects that his nongonococcal urethritis is due to a protozoan infection. What is the probable protozoal cause of the patient's nongonococcal urethritis?

Trichomonas vaginalis

A patient presents with difficulty breathing, malaise, weight loss, night sweats, and joint pain. Her medications include long-term steroid use. Clinical exam is consistent with pneumonia with multiple subcutaneous lesions on the forearms. What treatment do you recommend?

Trimethoprim-sulfamethoxazole

28-year-old woman presents with a 7-year history of AIDS. 1 month ago, her CD4 cell count was 48 cells/mm3 (stable over the past 3 months), and her viral load was detectable at 6,500 copies/mL. She feels well, and she is taking antiviral medication for her HIV infection. To date, she has not had any opportunistic infections. Based on her current CD4 cell count, what additional medication(s) should this patient be taking for prevention of opportunistic infections?

Trimethoprim/sulfamethoxazole and azithromycin

A Mexican immigrant presents with a few skin lesions on his face and on his body; they have been gradually growing over several years. The lesions are painless and non-itchy. On examination, there are 2 hypopigmented, hypoesthetic, well-bordered lesions on his face, and 2 more on his body. Biopsies taken from the lesions show chronic inflammation consisting of granulomas with lymphocytes, epithelioid cells, and foreign body giant cells. What is the most likely diagnosis?

Tuberculoid leprosy

35-year-old man has recently visited the medicine department with complaints of a 2-month history of abdominal pain. Pain is dull aching, intermittent, increases with hunger, and awakens the patient from sleep around 3 AM. Pain is partially relieved by bland food. He has a weight gain of about 3.5 kg. He gave a 2-week history of early morning nausea and vomiting. He has noticed blackish stool in the last 4 days. Early in the morning on the day of presentation, he experienced vomiting consisting of frank blood. On examination, his pulse rate is 110 beats/minute. Blood pressure 120/70 mm Hg, respiratory rate 18 breaths per minute, and temperature 37°C. Pallor is present, but there is no icterus, cyanosis, pedal edema, or clubbing. JVP is 8 cm of blood column. Otherwise, the general examination is normal. Abdominal examination reveals inverted umbilicus with no visible peristalsis or veins. There is mild epigastric tenderness but no guarding or rigidity. On percussion, there is no fluid in the peritoneum, and auscultation reveals normal bowel sounds. CVS, RS, and CNS examinations are normal. The rest of the examination is unremarkable. Lab investigation shows Hb -10.5 g% and occult blood in stool. Other investigations are within normal limits. He went for Upper GI endoscopy that showed peptic ulcer. At the time of endoscopy, a biopsy was also taken. It showed the presence of H. pylori on microscopy. What enzyme is most important for initiation of infection in this patient?

Urease

75-year-old man is brought to the Emergency Department with complaints of hematuria, abdominal pain, and fever. He denies any recent illness or travel. His medical history is significant for hypertension and diabetes. His symptoms began approximately 1 day ago and have been worsening with time. For the past few hours, he is experiencing burning during urination. His vital signs are as follows: Blood pressure 138/86 mmHg, pulse 66/min, respiration rate 12 per minute, temperature 99.2°F. His physical exam is normal. The most likely diagnosis is:

Urinary tract infection

35-year-old man was admitted to the hospital 10 days ago for shortness of breath. Chest X-ray showed lower lung consolidation, and he was diagnosed with pneumonia. He was treated with intravenous antibiotics with resolution of his cough and shortness of breath. He now has abdominal cramps and watery diarrhea. What is the most appropriate treatment?

Vancomycin

18-month-old child presents with a 2-day history of fever that is currently 101°F rectally. You symptomatically treat the patient and ask the mother to return if the condition worsens. The mother returns 2 days later because the child has developed small red spots that became bumps and are now blisters. The mother also noted the child was scratching the lesions. Physical exam reveals macules, papules, and vesicles are on the face and thorax bilaterally. Each vesicle resides on its own erythematous base. What is the most likely diagnosis?

Varicella

Following an uncomplicated pregnancy, a 34-year-old woman gives birth to a healthy boy. 2 days after birth, the woman develops a low-grade fever and vesicular lesions on her face and abdomen. History reveals an outbreak of chickenpox in her 2-year-old daughter's daycare facility. The mother is diagnosed with chickenpox. What is the best management for the newborn?

Varicella-zoster immune globulin

71-year-old man with a history of prostate cancer and unstable angina is admitted to a community hospital for facial cellulitis. Examination shows an indurated erythematous rash that extends across the face and zygomatic arch to the lip. In the oral cavity, vesicular lesions are present on the hard palate. Laboratory results are within normal ranges. The patient describes the lesions as very painful. A Tzanck smear of the vesicle showed multinucleated syncytial giant cells and intranuclear inclusion bodies. What is the most likely causative agent?

Varicella-zoster virus

36-year-old woman presents with a 24-hour history of sudden severe diarrhea described as profuse, gray, cloudy, watery stools without blood or fecal odor. She was recently in Bangladesh for work and returned yesterday, which was when the diarrhea began. She is also experiencing a mildly elevated temperature with a very dry mouth, headache, and severe fatigue. What is most likely offending organism?

Vibrio cholerae

36-year-old woman returning from a conference in Indonesia presents with profuse watery diarrhea. She reports having consumed fried rice, iced tea, and fruit at a street market several hours before her flight to the United States. The patient has 4 - 6 bowel movements daily, and they are preceded by cramps and nausea. She also has overwhelming thirst. Examination reveals dehydration, diaphoresis, orthostatic hypotension, and abnormal laboratory values for potassium (2.8 mmol/L). No leukocytes are seen in stool specimens, and cultures yield an oxidase-positive curved Gram-negative rod on blood and TCBS agar. What is the most likely etiology of the patient's illness?

Vibrio cholerae

26-year-old man with alcoholic cirrhosis suffers an injury on a shrimp boat in the Gulf of Mexico; his 3rd left finger is crushed under a metal pallet. The patient is treated in the emergency department for a fracture of the middle phalanx, and he is immunized against tetanus. The next day the patient returns to the emergency room; examination reveals a temperature of 38.5° C and hypotension. The patient's wound had become swollen, erythematous, and necrotic. Laboratory results confirm septicemia with a Gram-negative organism; selective media later identifies the etiologic agent. What organism is the most probable cause of the patient's illness?

Vibrio vulnificus

26-year-old woman presents for her second obstetric visit in the first trimester. Routine screening tests (blood typing, testing for syphilis, hepatitis, rubella immunity, and HIV) are performed; the test returns positive for HIV. She is counseled to start antiretroviral therapy and to have a cesarean delivery. To reduce the risk of mother-to-newborn transmission, the best drug treatment is a drug that prevents what mechanism of the infection?

Virus replication

30-year-old man who recently emigrated from Asia presents with a 2-week history of tingling and numbness in his hands and feet. 3 months ago, he visited a doctor after a 4-month history of weight loss, fever, productive cough, night sweats, and hemoptysis. After evaluation, he was diagnosed with tuberculosis and prescribed antitubercular medications, which he continues to take now. The addition of what vitamin to the patient's antitubercular regimen could have prevented his new symptoms?

Vitamin B6

18-year-old woman presents with a 3-day history of urinary frequency and foul-smelling urine. She does not recall having any fevers and/or chills. She does not have any back pain. All of her vitals are within normal limits. CBC is normal. A urinalysis is performed, and the results can be seen in the table. Urinalysis Test Result Color & Appearance Straw and hazy Specific gravity 1.010 PH 8 Leukocytes 1+ Nitrate Pos Protein Neg Glucose Neg Ketones Neg Urobilinogen Neg Bilirubin Neg Blood Neg Sediment Results 1+ bacteria 25 - 30 of image Refer to the image. For the presence of what is the image significant?

White blood cells

A 6-year-old boy presents with a 2-day history of fever and sore throat. On examination, the child has a fever of 39° C. He has enlarged, slightly tender cervical lymph nodes and a yellowish exudate over the tonsils. The spleen is enlarged 3 cm below the costal margin. His blood film reveals atypical lymphocytes and the heterophile antibody test is positive. The child is sent home with aspirin (500 mg tid) and advised to perform warm saline gargles 4 times a day. The child presents the next day with a fever of 40.5° C and is started on prednisone 50 mg/day. The following day the boy dies. What is the most likely diagnosis?

X-linked lymphoproliferative syndrome

32-year-old male patient presents with a subacute encephalitic prodrome including a two-week history of insomnia, headache, and vertigo, and is subsequently diagnosed with neurosyphilis. These symptoms may progress into a vascular stroke-like syndrome. Stroke-like symptoms are characteristic of what syndrome of neurosyphilis?

meningovascular