Infectious Disease — MCQs

A 3-year-old boy is brought to the physician by his mother because of a 2-week history of generalized fatigue, intermittent fever, and occasional bleeding from his nose. His temperature is 38.3°C (100.9°F). He appears pale. Physical examination shows cervical lymphadenopathy and multiple petechiae on his trunk. The spleen is palpated 3 cm below the left costal margin. His hemoglobin concentration is 9.3 g/dL, leukocyte count is 63,000/mm3, and platelet count is 30,000/mm3. A bone marrow aspirate predominantly shows immature leukocytes that stain positive for CD10, CD19, and terminal deoxynucleotidyl transferase (TdT), and negative for myeloperoxidase. Which of the following is the most likely diagnosis?

A 3-year-old boy is brought to the physician because of a 3-day history of fever and chills. The mother reports that he has also been limping for 2 days. He has no history of trauma to this region. His temperature is 38.9°C (102°F). Physical examination shows dull tenderness over his left lower extremity. The range of motion of the leg is also limited by pain. While walking, he avoids putting weight on his left leg. Laboratory studies show an erythrocyte sedimentation rate of 67 mm/h. An MRI is most likely to show abnormalities in which of the following regions?

A 14-year-old Somalian boy is brought to the emergency department by his mother because of a painful penile erection since he woke up 3 hours ago. His family recently emigrated to the United States from a refugee camp, and his past medical history is unknown. He has never had a health check up prior to this visit. On further questioning, his mother reports that the child is often fatigued and sick, and has episodes of joint pain. Examination shows ejection systolic murmurs heard over the precordium. Examination of the genitalia shows an engorged, tumescent penis. The remainder of the examination shows no abnormalities. Which of the following is the most likely underlying cause?

An 18-month-old toddler is brought to the pediatrician by her mother for cough. The mother reports that her daughter has had a productive-sounding cough and runny nose for the past 2 days. She has also noticed that her daughter feels warm. On chart review, this is the 4th time this patient is presenting for similar concerns; the 3 previous diagnoses were otitis media (2 episodes) and bacterial sinusitis (1 episode). Her temperature is 38.3°C (101.0°F). Physical examination is notable for cough and purulent sputum from both nares, although her lungs are clear to auscultation. Sputum gram stain shows gram-positive diplococci. Serum immunoglobulin studies show elevated levels of IgM and decreased levels of IgG and IgA. Which of the following is the most likely underlying diagnosis in this patient?

A 2-year-old girl presents with a rash on her body. Patient’s mother says she noticed the rash onset about 5 hours ago. For the previous 3 days, she says the patient has had a high fever of 39.0°C (102.2°F). Today the fever abruptly subsided but the rash appeared. Vitals are temperature 37.0°C (98.6°F), blood pressure 95/55 mm Hg, pulse 110/min, respiratory rate 30/min, and oxygen saturation 99% on room air. Physical examination reveals a maculopapular, non-confluent, blanchable rash on her back, abdomen, and chest extending superiorly towards the nape of the patient’s neck. Which of the following is this patient’s most likely diagnosis?

A 5-year-old African immigrant girl is brought to the office by her mother because she has had a fever and cough for the past month. They moved from Africa to the United States about 8 months ago. She denies any sore throat, rhinorrhea, diarrhea, or changes in appetite. Her mother says she has lost weight since her last visit 6 months ago for immunizations and a well-child visit. Previously, her weight was in the 36th percentile, but now she is in the 19th percentile. Her vital signs include: heart rate 75/min, respiratory rate 15/min, temperature 38.2°C (100.7°F), and blood pressure 110/76 mm Hg. Physical examination shows that the patient is breathing normally and has no nasal discharge. She has moderate non-tender cervical lymphadenopathy, bilaterally. On auscultation, there are diminished breath sounds from a right hemithorax. After the chest X-ray is ordered, which of the following is the most appropriate next step in management?

A previously healthy 2-year-old boy is brought to the emergency department because of a 36-hour history of fever and profuse, watery diarrhea. Several children at the child's daycare center have developed similar symptoms over the past few days. The patient has not received any routine childhood vaccines because his parents were afraid of associated side effects. He appears lethargic. His temperature is 38.1°C (100.6°F), pulse is 115/min, respirations are 25/min, and blood pressure is 90/58 mm Hg. Examination shows sunken eyes and dry mucous membranes. Capillary refill time is 3 seconds. Laboratory studies show: Hematocrit 52% Leukocyte count 9000/mm3 Platelet count 280,000/mm3 Serum Na+ 151 mEq/L K+ 3.2 mEq/L HCO3- 19 mEq/L Urea nitrogen 56 mEq/L Creatinine 1.0 mEq/L Glucose 90 mg/dL Which of the following is the most appropriate initial step in management?

A 5-year-old girl presents for a routine checkup. The patient’s parents say she has been looking pale and tired lately. Her family history is unremarkable. Upon physical examination, several bruises are seen, as well as petechial bleeding on her limbs. A complete blood count shows leukocytosis with severe anemia and thrombocytopenia. A peripheral blood smear shows 35% blasts. Ultrasonography of the abdomen shows hepatosplenomegaly and a chest radiograph reveals a mediastinal mass. Which of the following is the most likely diagnosis in this patient?

A 7-year-old girl is brought to the physician by her mother because of a 2-week history of generalized fatigue, intermittent fever, and progressively worsening shortness of breath. Physical examination shows pallor, jugular venous distention, and nontender cervical and axillary lymphadenopathy. Inspiratory stridor is heard on auscultation of the chest. The liver is palpated 3 cm below the right costal margin. Her hemoglobin concentration is 9.5 g/dL, leukocyte count is 66,000/mm³, and platelet count is 102,000/mm³. An x-ray of the chest shows a mediastinal mass. A bone marrow aspirate predominantly shows leukocytes and presence of 35% lymphoblasts. Which of the following additional findings is most likely in this patient?

A 16-year-old girl is brought to the physician for recurrent episodes of shortness of breath, nonproductive cough, and chest tightness for 3 months. These episodes occur especially while playing sports and resolve spontaneously with rest. She appears healthy. Her pulse is 63/min, respirations are 15/min, and blood pressure is 102/70 mm Hg. Pulse oximetry on room air shows an oxygen saturation of 98%. Physical examination shows no abnormalities. An x-ray of the chest shows no abnormalities. Spirometry shows a FEV1:FVC ratio of 85% and a FEV1of 85% of predicted. Which of the following is the most appropriate next step in management?