Common variable immunodeficiency

A 13-year-old girl is brought to her pediatricians office for evaluation of shortness of breath and cough. She has had two episodes of pneumonia over the last two years and an episode of bloody diarrhea six months ago requiring hospitalization. Two years ago, the patient was without any significant health complications. Her only past medical history is asthma. Family history is noncontributory. Her immunizations are up to date. Temperature is 38.7 C° (101.7 F°), pulse is 90/min, respirations are 25/min, and blood pressure is 100/60 mmHg. Height and weight are currently at the 5th percentile for age. Physical examination reveals faint rales over the right lower lung field. No enlarged lymph nodes are palpated on neck examination. Laboratory results are shown.

 

Laboratory value	Result
Complete blood count
Hemoglobin	12  g/dL
Leukocyte count	10,100 /mm3
Platelet count	200,000/mm3
Immunoglobulins
IgG	250mg/dL
IgA	24 mg/dL
IgM	15 mg/dL
IgE	undetectable
CD4/CD8 ratio	2 (normal, 1-4)

Chest x-ray reveals a right lower lobe infiltrate. Which of the following is the most likely diagnosis in this patient?