MEDizzy - A 1-year-old boy develops recurrent pneumonias and otitis

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Immunology

A 1-year-old boy develops recurrent pneumonias and otitis media. Examination reveals absence of tonsils, and no palpable lymph nodes. Lab tests reveal very low level (<2 standard deviations below the age-appropriate level) of IgG, IgM, IgA, and IgE. Peripheral blood flow cytometry demonstrates absence of circulating B cells. Of the following, the MOST likely diagnosis is

ExplanationFlow cytometry is an important test to demonstrate the absence of circulating B cells , which will distinguish X-linked agammaglobulinemia from most types of CVID, the hyper-IgM syndrome, and transient hypogammaglobulinemia of infancy.