Serum protein electrophoresis of a patient with recurrent sinopulmonary infections shows normal IgM but markedly reduced IgG and IgA. Peripheral blood B cells are normal in number. CD40L expression on T cells is normal. What is the most likely diagnosis?

• A X-linked agammaglobulinemia
• B Hyper-IgM syndrome type 1
• C Common variable immunodeficiency (CVID) ✓
• D Selective IgA deficiency

Explanation

CVID is characterized by low IgG, IgA, and IgM (though IgM may be near normal), normal or near-normal B-cell counts but failure to differentiate into plasma cells; it presents in the second or third decade with recurrent sino-pulmonary infections. XLA has absent B cells. Hyper-IgM syndrome type 1 has elevated IgM with absent IgG/IgA from CD40L defect, but CD40L is normal here. Selective IgA deficiency reduces only IgA.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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