Properly Identifying Pediatric Immunodeficiencies

In Episode 58 of Med School Question of the Week for USMLE, Faustine Ramirez, MedSchoolCoach expert tutor, answers this medical school question: A 2-year-old boy is brought to the pediatrician’s office with 3 days of fever, fatigue, and productive cough. He completed a course of antibiotics for acute otitis media two weeks ago, and has had frequent episodes of otitis media and thrush in the past year. His mother also reports easy bruising with very minor injuries and frequent nosebleeds. He was born at term following an uncomplicated pregnancy and delivery, although his mother recalls he developed prolonged bleeding following circumcision. He also has a history of severe eczema since infancy. He appears tired and irritable, but is consolable by his mother. Temperature is 38.7 C, heart rate is 135/min, respiratory rate is 38/min, and oxygen saturation is 94%. On examination he has mild sub-costal retractions and crackles are heard in the right lower lung fields. Multiple 1-2 cm mobile rubbery lymph nodes are palpable in the cervical chains, and there are white plaques on the tongue. An eczematous rash covers his face and body. A spleen tip is palpable 2 cm below the costal margin. Laboratory studies show the following:

• Hemoglobin – 12.5
• Leukocyte count – 4,800
• Platelet count – 42,000
• Blood smear: small platelet volume
• IgA – 490
• IgE – 420
• IgM – 50
• IgG – 630

Which of the following is the most likely diagnosis?

• Primary HIV infection
• Adenosine deaminase deficiency
• Hyper IgE syndrome
• Common variable immunodeficiency
• Wiskott-Aldrich syndrome
• X-linked severe combined immunodeficiency
• X-linked agammaglobulinemia