DERMATOLOGY-1

A 35-year-old man is brought to the emergency department 40 minutes after spilling hot oil on himself in a kitchen accident. Examination shows multiple tense blisters over the abdomen, anterior chest, and entire right leg. Deroofing of the blisters reveals tender and mottled underlying skin that does not blanch with pressure. Examination of the left thigh shows tender and erythematous skin with quick capillary refill after blanching with pressure. Which of the following is the closest estimate o

36%

A 3-year-old boy is brought to the physician for follow-up examination 5 daysafter sustaining a forehead laceration. Examination shows a linear, well-approximated laceration over the right temple. The wound is clean and dry with no exudate. There is a small amount of pink granulation tissuepresent. Microscopic examination of the wound is most likely to show which of the following?

Angiogenesis with type III collagen deposition

A 19-year-old woman comes to the physician because of a 2-week history of blue staining of her clothes when she exercises. She noticed that the stains are most prominent on her underwear and under her arms. She works as a professional ballet dancer and trains at least 15 hours per week. Her menstrual cycles occur at regular 28-day intervals. Physical examination shows black-blue discoloration of the skin in the axillae, areolae, and perineum. The remainder of the examination shows no abnormaliti

Apocrine

A previously healthy 24-year-old woman comes to the physician because of a 1-day history of painful rash after spending several hours in the sun. Skin examination shows well-demarcated areas of erythema with some scaling on the face, chest, upper back, and arms. The affected areas are hot and sensitive to touch. The oral mucosa appears normal. Which of the following is the most likely underlying mechanism of this patient's skin findings?

Apoptosis of keratinocytes in the epidermis

A 62-year-old man comes to the physician because of a 2-month history of an itchy rash and a 7-kg (15-lb) weight loss. Physical examination shows multiple erythematous plaques on the arms, legs, and chest. There are palpable lymph nodes in the axillary and inguinal areas. A biopsy of a skin lesion shows aggregates of neoplastic cells within the epidermis. A peripheral blood smear is most likely to show which of the following findings in this patient?

CD4+ cells with cerebriform nuclei

A 62-year-old woman with small-cell lung cancer comes to the physician because of a painful, burning red rash on her face and hands that developed 30 minutes after going outside to do garden work. She wore a long-sleevedshirt and was exposed to direct sunlight for about 10 minutes. The patient is light-skinned and has a history of occasional sunburns when she does not apply sunscreen. Current medications include demeclocycline for malignancy-associated hyponatremia and amoxicillin for sinusitis.

Cell injury due to drug metabolites

A 35-year-old man comes to the physician because of a rash on the thigh for 10 days. He reports that the rash has been enlarging and is intensely itchy. Two weeks ago, he adopted a stray dog from an animal shelter. Vital signs are within normal limits. A photograph of the examination findings is shown. Which of the following is the most likely cause of this patient's symptoms?

Dermatophyte infection

A 63-year-old man comes to the physician because of a 2-day history of fever and blood-tinged sputum. He has also had a productive cough for 1 year and has had 3 episodes of sinusitis during this time. Physical examination shows palpable erythematous skin lesions over his hands and feet that do not blanch on pressure. There are ulcerations of the nasopharyngeal mucosa and a perforation of the nasal septum. His serum creatinine is 2.6 mg/dL. Urinalysis shows acanthocytes, 70 RBCs/hpf, 2+ proteinu

Elevated c-ANCA titers

A 62-year-old woman with metastatic breast cancer comes to the physician because of a 2-day history of fever, chills, and new gluteal lesions. The lesions began as painless red macules and evolved into painful ulcers overnight. She received her fourth course of palliative chemotherapy 2 weeks ago. Her temperature is 38.2°C (100.8°F). Laboratory studies show a leukocyte count of 2,000/mm3 (20% segmented neutrophils). A photograph of one of the skin lesions is shown. Which of the following virul

Exotoxin A

A 19-year-old woman comes to the physician because of increased sweating for the past 6 months. She experiences severe sweating that is triggered by stressful situations and speaking in public. She is failing one of her university classes because of her avoidance of public speaking. She has not had any fevers, chills, weight loss, or night sweats. Her temperature is 36.6°C (98°F). Physical examination shows moist skin in the axillae and on the palms, soles, and face. Which of the following dru

Glycopyrrolate

A 43-year-old woman comes to the physician because of a 1-day history of rash on the trunk and lower extremities. Three days ago, she visited a spa resort with multiple swimming pools and whirlpools. A friend of hers who also visited the spa has developed a similar rash. She does not smoke or drink alcohol and takes no medications. She appears well. Her vital signs are within normal limits. Examination shows multiple erythematous, excoriated papules, and pustules over the trunk and upper thighs.

Hair follicles

An investigator studying immune response administers a 0.5 mL intradermal injection of an autoclaved microorganism to a study volunteer. Four weeks later, there is a 12-mm, indurated, hypopigmented patch over the site of injection. Which of the following is the most likely explanation for the observed skin finding?

Increased activity of CD4+ Th1 cells

One week after admission to the hospital for burns sustained in a building fire, a 24-year-old man undergoes evaluation for the feasibility of skin grafting. Physical examination shows third-degree burns on his entire torso, left arm, and head. Urine and blood cultures grow no organisms. A chest x-rayshows no abnormalities. Compared with a healthy adult, which of the following changes are most likely to be seen in this patient at this time?

Increased resting energy expenditure

A 27-year-old man is brought to the emergency department shortly after sustaining injuries in a building fire. On arrival, he appears agitated and has shortness of breath. Examination shows multiple second-degree burns over the chest and abdomen and third-degree burns over the upper extremities. Treatment with intravenous fluids and analgesics is begun. Two days later, the patient is confused. His temperature is 36°C (96.8°F), pulse is 125/min, and blood pressure is 100/58 mm Hg. Examination s

Inhibition of protein synthesis

A 74-year-old man comes to the physician for evaluation of a skin lesion on his right arm. The lesion first appeared 3 months ago and has since been slowly enlarging. Physical examination shows a 1.5-centimeter, faintly erythematous, raised lesion with irregular borders on the dorsum of the right forearm. A biopsy specimen is obtained. If present, which of the following histopathological features would be most consistent with carcinoma in situ?

Irreversible nuclear changes in the stratum basale

A 32-year-old man comes to the physician because of a 1-week history of fever, nausea, headache, and confusion. Three weeks ago, he had an episode of a sore throat, diarrhea, and generalized lymphadenopathy. He is sexually active with a new partner that he met 2 months ago and they use condoms inconsistently. He appears ill. Physical examination shows nuchal rigidity. Further evaluation shows infection with an enveloped, single-stranded, positive-sense RNA virus. The cells most likely affected i

Langerhans cells

A 76-year-old woman comes to the physician for a 3-day history of swelling and redness of her left lower leg. She has type 2 diabetes mellitus and hypertension. Her temperature is 38.7ºC (101.7ºF). Examination of the left leg shows an erythematous, raised skin lesion with sharply demarcated margins. The affected skin is warm and tender to palpation. A diagnosis of cutaneous streptococcal infection is made. In addition to the upper dermis, the patient's condition is most likely to involve tissu

Mesoderm

A 47-year-old woman comes to the physician because of a 1-month history of progressive weakness. She has had increased difficulty climbing stairs and standing from a seated position. She takes no medications. Neurologic examination shows weakness of the proximal muscles. Skin examination shows diffuse erythema of the upper back, posterior neck, and shoulders. A photograph of the patient's eye is shown. Antibodies against which of the following are most likely to be present in this patient?

Mi-2 protein

A 48-year-old man comes to the physician because of a hypopigmented skin lesion on his finger. He first noticed it 4 weeks ago after cutting his finger with a knife while preparing food. He did not feel the cut. For the past week, he has also had fever, fatigue, and malaise. He has not traveled outside the country since he immigrated from India to join his family in the United States 2 years ago. His temperature is 38.7°C (101.7°F). Physical examination shows a small, healing laceration on the

Mycobacterium leprae

A 30-year-old man comes to the physician for a follow-up examination 1 month after sustaining a chemical burn over the dorsum of his right hand and forearm. Physical examination shows hyperextension of the hand at the wrist. The skin over the dorsum of the wrist is tense and there is a thick, epithelialized scar. Range of motion of the right wrist is restricted. This patient's contracture is most likely due to activity of which of the following cells?

Myofibroblasts

An investigator is studying the immunologic response to a Staphylococcus aureus toxin in a mouse model. Fourteen days after injecting mice with this toxin, he isolates antibodies against neutrophil proteinase 3 in their serum. A patient with high concentrations of these antibodies would most likely present with which of the following clinical features?

Nasal mucosal ulcerations and hematuria

A 56-year-old woman comes to the physician because of a 3-month history of progressive weakness. She has no history of serious illness and takes no medications. Her vital signs are within normal limits. Physical examination shows a violaceous rash over her eyelids. A photograph of her hands is shown. Muscle strength is 4/5 at the shoulders and hips but normal elsewhere. This patient is at greatest risk for which of the following conditions?

Ovarian adenocarcinoma

A 3400-g (7-lb 8-oz) newborn is delivered at 40 weeks' gestation. Physical examination shows pale skin, blond hair, and blue irides. Her parents are from Haiti and express concern, as the newborn's appearance contrasts greatly with their own. The most likely cause of this newborn's condition is a defect in which of the following processes?

Oxidation of dihydroxyphenylalanine

A 42-year-old woman comes to the physician because of a 2-month history of progressive muscular weakness. She has had difficulty climbing stairs, getting up from chairs, and brushing her hair. Her vital signs are within normal limits. Muscle strength is 2/5 with flexion of the hips and 3/5 with abduction of the shoulders. She is unable to stand up from her chair without the use of her arms for support. Laboratory studies show elevations in leukocyte count, erythrocyte sedimentation rate, and cre

Sarcolemmal MHC-I overexpression with CD8+ lymphocytic infiltration

A 3-year-old boy is brought to the emergency department because of nausea and vomiting for 1 day. His maternal uncle had a seizure disorder and died in childhood. He appears fatigued. Respirations are 32/min. Examination shows diffuse weakness in the extremities. Serum studies show a low pH, elevated lactate concentration, and normal blood glucose. A metabolic condition characterized by a defect in oxidative phosphorylation is suspected. Microscopic examination of a muscle biopsy specimen of thi

Subsarcolemmal accumulation of mitochondria

A 44-year-old man is brought to the emergency department by a coworker 2 hours after accidentally burning his foot on an electric grill that he keeps next to his bed because he likes to wake up to the smell of bacon. He initially decided to go to work despite his injury but felt like it was "too serious to ignore." He is the regional manager of a paper company. His vital signs are within normal limits. Examination of his right foot shows erythematous skin with multiple blisters, some of whic

Superficial partial-thickness burn

A 44-year-old woman with type 2 diabetes mellitus comes to the physician with a 3-day history of fever, right calf pain, and swelling. Her temperature is 38.7°C (101.7°F). Physical examination shows a 5 x 6-cm erythematous, warm, raised skin lesion with well-defined margins over the right upper posterior calf. The organism isolated from the lesion forms large mucoid colonies on blood agar. Further evaluation shows that the organism has a thick hyaluronic acid capsule. The causal organism of th

Susceptibility to bacitracin

A 36-year-old man comes to the physician because of a 2-day history of malaise and a painful, pruritic rash on his lower back and thighs. His temperature is 37.8°C (100°F). Physical examination shows the findings in the photograph. Skin scrapings from the thigh grow neutral colonies on MacConkey agar. The colony-producing bacteria are oxidase-positive. Which of the following is the strongest risk factor for the patient's condition?

Swimming in pool

A 59-year-old man comes to the physician because of a 4-month history of a pruritic rash. His symptoms have not improved despite treatment with over-the-counter creams. During this period, he has also had a 6-kg (13.5-lb) weight loss. Examination shows a scaly rash over his chest, back, and thighs. A photograph of the rash on his thighs is shown. A biopsy of the skin lesions shows clusters of neoplastic cells with cerebriform nuclei within the epidermis. This patient's condition is most likely c

T cells

A 26-year-old woman comes to the physician 6 months after delivering a baby by lower segment transverse cesarean section. She is worried about the appearance of her cesarean section scar. Examination shows a linear, erythematous, raised suprapubic scar, confined within the original wound margins. Biopsy of the scar shows dense collagen fibers organized parallel to the surface of the epidermis. An increase in the production of which of the following mediators is most likely responsible for the ch

Transforming growth factor-beta

A 28-year-old African American woman delivers her first child at 39 weeks'gestation. On examination, the newborn's skin and hair have a milky white color, and his eyes are light blue with a slight reddish hue. A skin biopsy shows a normal number of epidermal and follicular melanocytes. The physician advises the parents that the child will need a comprehensive eye examination and genetic testing to establish the suspected diagnosis. A defect in which of the following enzymes is the most likely ca

Tyrosinase