Chapters 28-31
4. In a full-term infant, the normal erythrocyte life span is days, whereas the adult erythrocyte life span is days.
60-80; 120
The student studying pathophysiology learns which facts about leukemias? (Select all that apply.) a. A single progenitor cell undergoes a malignant change. b. Leukemia is a result of uncontrolled cellular proliferation. c. Bone marrow becomes overcrowded. d. Leukocytes are under produced. e. Hematopoietic cell production is decreased.
A SIngle progenitor cell undergoes a malignant change, Leukemia is a result of uncontrolled cellular proliferation, Bone Marrow becomes overcrowded, Hematopoietic cell production is decreased
23. When the demand for mature neutrophils exceeds the supply, immature neutrophils are released indicating:
A shift to the left
Which statements are true regarding leukemias? (Select all that apply.) a. A single progenitor cell undergoes a malignant change. b. Leukemia is a result of uncontrolled cellular proliferation. c. Bone marrow becomes overcrowded. e. Hematopoietic cell production is decreased.
A single progenitor cell undergoes a malignant change, Leukemia is a result of uncontrolled cellular proliferation, Bone marrow becomes over crowed, Hematopoietic cell production is decreased
What are the clinical manifestations of advanced non-African Burkitt lymphoma? (Select all that apply.)
Abdm. swelling, night sweats and Fever
What are the clinical manifestations of advanced non-African Burkitt lymphoma? (Select all that apply.) a. Abdominal swelling b. Night sweats c. Fever d. Weight gain e. Dementia
Abdmn. swelling, Night sweats, Fever
Which of the following is characterized by what is referred to as pathognomonic pentad of symptoms?
Acute idiopathic thrombotic thrombocytopenic purpura
A 2000 ml blood loss will produce which assessment finding? (Select all that apply.) a. Air hunger b. Normal blood pressure in the supine position c. Rapid thready pulse d. Cold clammy skin e. lactic acidosis
Air hunger, rapid thready pulse, cold clammy skin
What are the most significant risk factors for the development of thrombus formation as referred to by the Virchow triad? (Select all that apply.) a. Endothelial injury to blood vessels b. Turbulent arterial blood flow c. Rapid coagulation of the blood d. Stagnant venous blood flow
All of the above
Early detection of acute leukemia would include which symptoms? (Select all that apply.) a. Dizziness b. Paresthesia c. Anorexia d. Bruising e. Bone pain
Anorexia, Bruising, Bone pain
Normocytic-normochromic anemia
Aplastic anemia
5. Which description is consistent with chronic lymphocytic leukemia
B cells fail to mature into plasma cells that synthesize immunoglobulins.
A student studying microbiology learns which facts about the Epstein-Barr virus (EBV)? (Select all that apply.) a. Causative organism for infectious mononucleosis b. Rare mutation may be seen in Burkitt Lymphoma. c. Implicated in some nasopharyngeal cancers d. Is only seen along with rare non-Hodgkin lymphomas e. Immunodeficiency can lead to EBV-positive neoplasms.
Causative organism for infectious mononucleosis, Implicated in some Nasopharyngeal cancers, and Immunodeficiency can lead to EBV-positive neoplasms.
Which medications are associated with an intermediate increase in a person's risk for developing aplastic anemia? (Select all that apply.) a. Penicillin b. Chloramphenicol (Chloromycetin) c. Phenytoin (Dilantin) d. Trimethoprim-sulfamethoxazole (Bactrim) e. Thiazides
Chloramphenicol, Phenytoin, Trimethoprim-sulfamethoxazole
. Diagnosed by the Philadelphia chromosome
Chronic myelogenous leukemia
Immune thrombocytopenia (ITP) is a(n) ____________condition in adults and a(n)____________condition in children.
Chronic; acute
What is the most reliable and specific test for diagnosing disseminated intravascular coagulation (DIC)?
D-dimer
Which disorder is described as an unregulated release of thrombin with subsequent fibrin formation and accelerated fibrinolysis?
Disseminated intravascular coagulation (DIC)
What change is observed in leukocytes during an allergic disorder (type I hypersensitivity) often caused by asthma, hay fever, and drug reactions?
Eosinophelia
Why does fetal hemoglobin have a greater affinity for oxygen than adult hemoglobin?
Fetal hemoglobin interacts less readily with diphosphoglycerate (DPG), which inhibits hemoglobin-oxygen binding.
What are the clinical manifestations of folate deficiency anemia? (Select all that apply.) a. Constipation b. Flatulence c. Dysphagia d. Stomatitis e. Cheilosis
Flatulence, Dysphagia, Stomatitis, cheilosis
How does hemolytic disease of the newborn (HDN) cause acquired congenital hemolytic anemia?
HDN is an alloimmune disease in which the mother's immune system produces antibodies against fetal erythrocytes, which are recognized as foreign and removed from circulation.
A healthcare professional is caring for five patients. Which one would the professional assess for disseminated intravascular coagulation (DIC) as the priority? (Select all that apply.) a. Heat stroke b. Severe pancreatitis c. Term delivery d. HELLP syndrome e. Snake bite
Heat Stroke. Severe pancreatitis, HELLP Syndrome, Snake Bite
Diagnosed by the Reed-Sternberg cell
Hodgkin lymphoma
6. Which electrolyte imbalance accompanies multiple myeloma (MM)?
Hypercalcemia
11. Which statement best describes heparin-induced thrombocytopenia (HIT)?
Immunoglobulin G immune-mediated adverse drug reaction that reduces circulating platelets
What is the cause of polycythemia in the fetus?
Increased erythropoiesis occurs in response to the hypoxic intrauterine environment.
What is the most common cause of insufficient erythropoiesis in children?
Iron Deficiency
13. Vitamin_____ is required for normal clotting factor synthesis by the_______ .
K; liver
Which classic clinical manifestations are symptoms of infectious mononucleosis (IM)? (Select all that apply.) a. Lymph node enlargement b. Hepatitis c. Pharyngitis d. Edema in the area of the eyes e. Fever
Lymph node enlargement, Pharyngitis, Fever
Which blood cell type is elevated at birth but decreases to adult levels during the first year of life?
Monocytes
Which statement relates to immune thrombocytopenic purpura (ITP)?
Mononuclear phagocytes in the spleen remove antibody-coated platelets from circulation.
Bence Jones protein
Multiple myeloma
Macrocytic-normochromic anemia
Pernicious anemia
The two major forms of leukemia, acute and chronic, are classified by which criteria?
Predominate cell type and Rate of progression
10. Which term is used to describe a red-purple discoloration caused by diffuse hemorrhage into the skin tissue?
Purpura
Which diseases are commonly associated with anemia of chronic disease? (Select all that apply.) a. Rheumatoid arthritis b. Acquired immunodeficiency syndrome (AIDS) c. Polycythemia vera d. Systemic lupus erythematosus e. Chronic hepatitis
RA, AIDS, Systemic Lupus erythematosus, Chronic hepatitis
Hodgkin disease is characterized by the presence of which of the following?
Reed-Sternberg (RS) cells
Microcytic-hypochromic anemia
Sideroblastic anemia
In disseminated intravascular coagulation (DIC), what are the indications of microvascular thrombosis?
Symmetric cyanosis of fingers and toes
A patient has splenomegaly on physical examination. What does the healthcare professional understand about this condition? (Select all that apply.) a. It may be normal so nothing further needs to be done b. The patient may have an acute infection. c. Splenomegaly can lead to hepatic failure. d. Tumors or cysts can cause splenomegaly. e. Some infiltrative processes can cause it.
The patient may have an acute infection, Tumors or cysts can cause splenomegaly, and some infiltrative processes can cause it.
A person has lab drawn and the white blood cell count is much higher than normal. The healthcare professional understands which facts about this finding? (Select all that apply.) a. The person has leukocytosis. b. The person has leukopenia. c. The person may have an infection. d. The person may have a myeloproliferative disorder. e. The person needs a bone marrow biopsy
The person has luekocytosis, The person may have an infection, The person may have a myeloproliferative disorder
What term is used to identify thrombi that occlude arterioles and capillaries and are made up of platelets with minimal fibrin and erythrocytes?
Thrombotic thrombocytopenic purpura (TTP)
In disseminated intravascular coagulation (DIC), what activates the coagulation cascade?
Tissue factor (TF) located in the endothelial layer of blood vessels and subcutaneous tissue
What is the most common cause of vitamin K deficiency?
Total parenteral nutrition with antibiotic therapy
Which proinflammatory cytokines are responsible for the development and maintenance of disseminated intravascular coagulation (DIC)?
Tumor necrosis factor-alpha (TNF-); IL-1, IL-6, and IL-8; and platelet- activating factor (PAF)
Considering iron replacement therapy prescribed for iron deficiency anemia, who is likely to require long-term daily maintenance dosage? a. A woman who has not yet experienced menopause b. A teenager who is involved in strenuous athletics c. A middle-aged man who smokes two packs of cigarettes a day d. An older person demonstrating signs of dementia
a. A woman who has not yet experienced menopause
A patient has been diagnosed with acute lymphocytic leukemia (ALL) and asks the healthcare professional to describe it. What description by the professional is most accurate? a. ALL is a progressive neoplasm defined by the presence of greater than 30% lymphoblasts in the bone marrow or blood. b. In ALL, immature blasts cells replace normal myelocytic cells, megakaryocytes, and erythrocytes. c. B cells fail to mature into plasma cells that synthesize immunoglobulins. d. The translocation of genetic material from genes 9 and 22 create an abnormal, fused gene identified as BCR-ABL.
a. ALL is a progressive neoplasm defined by the presence of greater than 30% lymphoblasts in the bone marrow or blood
Which statement best describes a Schilling test? a. Administration of radioactive cobalamin and the measurement of its excretion in the urine to test for vitamin B12 deficiency b. Measurement of antigen-antibody immune complexes in the blood to test for hemolytic anemia c. Measurement of serum ferritin and total iron-binding capacity in the blood to test for iron deficiency anemia d. Administration of folate and measurement in 2 hours of its level in a blood sample to test for folic acid deficiency anemia.
a. Administration of radioactive cobalamin and the measurement of its excretion in the urine yo test for vitamin B12 deficiency
A student asks the professor what the most common pathophysiologic process is that triggers aplastic anemia (AA). What response by the professor is most accurate? a. Autoimmune disease against hematopoiesis by activated cytotoxic T (Tc) cells b. Malignancy of the bone marrow in which unregulated proliferation of erythrocytes crowd out other blood cells c. Autoimmune disease against hematopoiesis by activated immunoglobulins d. Inherited genetic disorder with recessive X-linked transmission
a. Autoimmune disease against hematopoeisis by activated cytotoxic T (Tc) cells
A student is learning about the functions of leukocytes. What statements about these cells are correct? (Select all that apply.) a. Eosinophilia can result from parasitic infections. b. Basophilia can be seen in hypersensitivity reactions. c. Monocytosis is usually seen in acute infections. d. Lymphocytosis occurs rapidly in bacterial infections. e. Granulocytopenia can be a life-threatening condition.
a. Eosinophilia can result from parasitic infections, b. Basophilia can be seen in hypersensitivity reactions e. Granulocytopenia can be life-threatening condition
A healthcare professional is reviewing a patient's laboratory results and sees that the patient has a low reticulocyte count and a high iron level. Which type of anemia does the professional associate these findings with? a. Folate deficiency anemia b. Iron deficiency anemia c. Hemolytic anemia d. Anemia of chronic disease
a. Folate deficiency anemia
A healthcare professional has educated a student on folic acid. Which statement by the student indicates that more teaching is needed? a. Folic acid absorption is dependent on the enzyme folacin. b. Folic acid is stored in the liver. c. Folic acid is essential for RNA and DNA synthesis within erythrocytes. d. Folic acid is absorbed in the upper small intestine.
a. Folic acid absorption is dependent on the enzyme folacin
A hospitalized patient's lab work is as follows: WBC 2000, bands 14.8%, and segmented neutrophils 5. The healthcare professional calculates the patient's absolute neutrophil count (ANC). What action does the professional take next? a. Implements protocols to prevent life-threatening infections b. Encourages the patient to limit any visitors for the present time c. Does nothing; this is a normal ANC for the white cell count d. Holds the patient's medications until the ANC returns to normal
a. Implements protocols to prevent life-threatening infections
Which of these describes how the body compensates for anemia? a. Increasing rate and depth of breathing b. Decreasing capillary vasoconstriction c. Hemoglobin holding more firmly onto oxygen d. Kidneys releasing more erythropoietin
a. Increase rate and depth of breathing
A person comes to the healthcare clinic and reports night sweats and fever. The healthcare professional obtains a chest x-ray which shows a mediastinal mass. What other assessment or diagnostic test does the professional provide as a priority? a. Listen to heart sounds. b. Assess the patient's skin. c. Arrange for familial DNA testing. d. Test blood for anemia
a. Listens to heart sounds
Sideroblastic anemia can occasionally result from an autosomal recessive transmission inherited from which relative? a. Mother c. Grandfather b. Father d. Grandmother
a. Mother
A patient is 8 hours postoperative after a long orthopedic procedure. The student asks why this patient is at particular risk of developing a thromboembolism. What response by the healthcare professional is best? a. Patients tend to have venous stasis from orthopedic operations. b. Anesthetic agents often cause an immune response against clotting factors. c. Endothelial damage occurs and repair is slowed by postoperative pain. d. Atherosclerotic build up causes turbulent blood flow leading to clots
a. Patients tend to have venous stasis from orthopedic operations
Considering sideroblastic anemia, what would be the expected effect on the plasma iron levels? a. Plasma iron levels would be high. b. Levels would be low. c. Levels would be normal. d. Levels would be only minimally affected.
a. Plasma iron levels would be high
The two major forms of leukemia, acute and chronic, are classified by which criteria? (Select all that apply.) a. Predominant cell type b. Rate of progression c. Age of individual when cells differentiation occurs d. Stage of cell development when malignancy first occurs e. Serum level of leukocytes
a. Predominant cell type, b. Rate of progression
How is the effectiveness of vitamin B12 therapy measured? a. Reticulocyte count b. Serum transferring c. Hemoglobin d. Serum vitamin B12
a. Reticulocyte count
An adult patient has been hospitalized with thrombocytopenia with a platelet count of 8000/mm3 . What action by the healthcare professional is most appropriate? a. Tell the patient not to get out of bed without assistance. b. Prepare the patient for transfusions of whole blood. c. Educate the patient on side effects of heparin. d. Nothing; this finding is normal in an adult.
a. Tell the patient not to get out of bed without assistance
What does treatment for polycythemia vera involve? a. Therapeutic phlebotomy and radioactive phosphorus b. Restoration of blood volume by plasma expanders c. Administration of cyanocobalamin d. Blood transfusions
a. Therapeutic phlebotomy and radioactive phosphorus
A healthcare professional in an urban clinic is seeing a patient who has iron deficiency anemia (IDA). What question by the professional is most appropriate to assess for the cause of IDA? a. "How many times a week do you have iron-rich foods?" b. "Have you ever noticed any blood in your stool?" c. "Do you have a history of heart valve replacement?" d. "Have you had any recent viral infections?"
b. "Have you ever noticed any blood in your stool?"
A patient has been hospitalized for a large deep vein thrombosis and states he is the third person in his family to have this condition in the last 2 years. What response by the healthcare professional is most appropriate? a. "This condition is not transmitted genetically." b. "We can test your blood for factor V Leiden." c. "Were they all men or both men and women?" d. "Familial thromboses tend to be very severe."
b. "We can test your blood for factor V Leiden."
An allogenic bone marrow transplantation remains the preferred method for treating which anemia? a. Polycythemia vera b. Aplastic c. Sideroblastic d. Anemia of chronic disease (ACD)
b. Aplastic
A healthcare professional works with recent refugees. A mother brings in her children who have been diagnosed with iron deficiency anemia. What action by the professional is most appropriate? a. Educate the mother on an iron-rich diet. b. Arrange to test for parasitic infections. c. Explain the weekly iron infusions. d. Teach the mother to give iron supplements.
b. Arrange to test for parasitic infections
What is the most common cause of iron deficiency anemia (IDA)? a. Decreased dietary intake b. Chronic blood loss c. Vitamin deficiency d. Autoimmune disease
b. Chronic blood loss
A student asks the professor to explain the jaundice that accompanies hemolytic anemia. Which statement is by the professor is most accurate? a. Erythrocytes are destroyed in the spleen. b. Heme destruction exceeds the liver's ability to conjugate and excrete bilirubin. c. The patient has elevations in aspartate transaminase (AST) and alanine transaminase (ALT). d. The erythrocytes are coated with an immunoglobulin.
b. Heme destruction exceeds the liver's ability to conjugate and excrete bilirubin
In infectious mononucleosis (IM), what does the Monospot test detect? a. Immunoglobulin E (IgE) b. Immunoglobulin M (IgM) c. Immunoglobulin G (IgG) d. Immunoglobulin A (IgA)
b. IgM
Which type of anemia is characterized by fatigue, weakness, and dyspnea, as well as conjunctiva of the eyes and brittle, concave nails? a. Pernicious c. Aplastic b. Iron deficiency d. Hemolytic
b. Iron deficiency
The paresthesia that occurs in vitamin B12 deficiency anemia is a result of which of these? a. Reduction in acetylcholine receptors in the postsynaptic nerves b. Myelin degeneration in the spinal cord c. Destruction of myelin in peripheral nerves d. Altered function of neurons in the parietal lobe
b. Myelin degeneration in the spinal cord
A patient in the healthcare clinic reports fatigue, weakness, and dyspnea, as well as pale conjunctiva of the eyes and brittle, concave nails. What assessment by the healthcare professional is most appropriate for the suspected anemia? a. Blood pressure and apical pulse b. Oral mucus membranes and tongue c. Ability to swallow foods and liquids d. Skin and sclera for normal coloration
b. Oral mucus membranes and tongue
The underlying disorder of which anemia is a result of the defective secretion of the intrinsic factor, which is essential for the absorption of vitamin B12? a. Microcytic c. Hypochromic b. Pernicious d. Hemolytic
b. Pernicious
Which of these classified as a megaloblastic anemia? a. Iron deficiency b. Pernicious c. Sideroblastic d. Hemolytic
b. Pernicious
Local signs and symptoms of Hodgkin disease-related lymphadenopathy are a result of what? a. Pressure and ischemia b. Pressure and obstruction c. Inflammation and ischemia d. Inflammation and pressure
b. Pressure and obstruction
A patient is admitted to the hospital with multiple myeloma (MM). Which diagnostic test should the healthcare professional assess as the priority? a. Serum potassium level b. Serum calcium level c. Bone scan or limb x-rays d. Bone marrow biopsy
b. Serum calcium level
In aplastic anemia (AA), pancytopenia develops as a result of what? a. Suppression of erythropoietin to produce adequate amounts of erythrocytes b. Suppression of the bone marrow to produce adequate amounts of erythrocytes, leukocytes, and thrombocytes c. Lack of DNA to form sufficient quantities of erythrocytes, leukocytes, and thrombocytes d. Lack of stem cells to form sufficient quantities of leukocytes
b. Suppression of the bone marrow to produce adequate amounts of erythrocytes, leukocytes, and thrombocytes
A patient has defective secretion of the intrinsic factor leading to anemia. What treatment option does the healthcare professional discuss with the patient? a. Increasing iron sources in the diet such as red meat. b. Vitamin B12 injections initially given once a week. c. Having relatives tested for bone marrow donation. d. Better control of the patient's underlying disorder.
b. Vitamin B12 injections initially given once a week
A person has been diagnosed with acute lymphocytic leukemia (ALL) that is positive for the Philadelphia chromosome. What statement by the healthcare professional is most appropriate? a. "This is good news and means the ALL is not very aggressive." b. "This is a very rare finding in adults who have ALL." c. "We are planning to get your disease in remission, but it will be hard." d. "You will need colony-stimulating support during your treatment."
c. "We are planning to get your disease in remission, but it will be hard."
Shortened erythrocyte life span, ineffective bone marrow response to erythropoietin, and altered iron metabolism describe the pathophysiologic characteristics of which type of anemia? a. Aplastic b. Sideroblastic c. Anemia of chronic disease d. Iron deficiency
c. Anemia of chronic disease
What term is used to describe the capacity of some erythrocytes to vary in size, especially in relationship to some anemias? a. Poikilocytosis b. Isocytosis c. Anisocytosis d. Microcytosis
c. Anisocytosis
What term is used to describe the capacity of some erythrocytes to vary in size, especially in relationship to some anemias? a. Poikilocytosis c. Anisocytosis b. Isocytosis d. Microcytosis
c. Anisocytosis
Reed-Sternberg (RS) cells represent malignant transformation and proliferation of which of these? a. Interleukin (IL)-1, IL-2, IL-5, and IL-6 b. Tumor necrosis factor-beta c. B cells d. T cells
c. B cells
The students learn that deficiencies in folate and vitamin B12 alter the synthesis of which of these? a. RNA b. Cell membrane c. DNA d. Mitochondria
c. DNA
What does the student learn about warm autoimmune hemolytic anemia? a. Warm autoimmune hemolytic anemia occurs primarily in children. b. It is self-limiting and rarely produces hemolysis. c. Erythrocytes are bound to macrophages and sequestered in the spleen. d. Immunoglobulin M coats erythrocytes and binds them to receptors on monocytes
c. Erythrocytes are bound to macrophages and sequestered in the spleen
Which condition resulting from untreated pernicious anemia (PA) is fatal? a. Brain hypoxia b. Liver hypoxia c. Heart failure d. Renal failure
c. Heart Failure
A patient has hepatomegaly, bronze-colored skin, and cardiac dysrhythmias. What condition does the healthcare professional prepare to teach the patient about? a. Aplastic anemia b. Pernicious anemia c. Hereditary hemochromatosis d. Immune thrombocytopenia purpura
c. Hereditary hemochromatosis
What is the fundamental physiologic manifestation of anemia? a. Hypotension b. Hyperesthesia c. Hypoxia d. Ischemia
c. Hypoxia
A patient has polycythemia vera and presents to the Emergency Department with plethora and neurological changes. The student asks the healthcare professional to explain the primary cause of these symptoms. What response by the professional is best? a. Decreased erythrocyte count b. Destruction of erythrocytes c. Increased blood viscosity d. Tissue destruction by macrophages
c. Increased blood viscosity
Which anemia produces small, pale erythrocytes? a. Folic acid b. Hemolytic c. Iron deficiency d. Pernicious
c. Iron deficiency
A patient in the hospital has been receiving heparin injections. The platelet count on admission was 222,000/mm3 and four days later is 113,000/mm3 . What action by the healthcare professional is best? a. Prepare to transfuse the patient with platelets. b. Do nothing; this is an expected side effect. c. Switch the heparin to lepirudin d. Stop all the patient's medications
c. Switch the heparin to lepirudin
Which virus is associated with Burkitt lymphoma in African children? a. Cytomegalovirus b. Adenovirus c. Human papillomavirus d. Epstein-Barr virus
d. Epstein-Barr Virus
After a person has a subtotal gastrectomy for chronic gastritis, which type of anemia will result? a. Iron deficiency b. Aplastic c. Folic acid d. Pernicious
d. Pernicious
What causes the atrophy of gastric mucosal cells that result in pernicious anemia? a. Erythrocyte destruction b. Folic acid malabsorption c. Vitamin B12 malabsorption d. Poor nutritional intake
d. Poor Nutritional intake
Which statement is true regarding the physical manifestations of vitamin B12 deficiency anemia? a. Vitamin B12 deficiency anemia seldom results in neurologic symptoms. b. The chances of a cure are good with appropriate treatment. c. The condition is reversible in 75% of the cases. d. Symptoms are a result of demyelination.
d. Symptoms are a result of demyelination
Continued therapy of pernicious anemia (PA) generally lasts how long? a. 6 to 8 weeks c. Until the iron level is normal b. 8 to 12 months d. The rest of one's life
d. The rest of one's life
Which description is consistent with chronic myelogenous leukemia (CML)? a. Defects exist in the ras oncogene, TP53 tumor-suppressor gene, and INK4A, the gene encoding a cell-cycle regulatory protein. b. Leukocytosis and a predominance of blast cells characterize the bone marrow and peripheral blood. As the immature blasts increase, they replace normal myelocytic cells, megakaryocytes, and erythrocytes. c. B cells fail to mature into plasma cells that synthesize immunoglobulins. d. The translocation of genetic material from genes 9 and 22 creates an abnormal, fused protein identified as BCR-ABL1.
d. The translocation of genetic material from genes 9 and 22 creates an abnormal fused protein identified as BCR-ABL1
A healthcare professional is evaluating laboratory results for a patient who has disseminated intravascular coagulation (DIC). What results would the professional consider consistent with this condition? (Select all that apply.) a. Elevated d-dimer b. Elevated creatinine c. Decreased protein C d. Decreased lactate dehydrogenase e. Increased pH
elevated d-dimer, Elevated creatinine, Decreased protein C
Epstein-Barr virus
infectious mononucleosis