A 28-year-old woman with a history of recurrent sinopulmonary infections presents with chronic diarrhea and weight loss. Endoscopy reveals nodular lymphoid hyperplasia in the small intestine. Serum IgG is 280 mg/dL, IgA is 15 mg/dL, and IgM is 20 mg/dL. B cells are present in normal numbers but do not differentiate into plasma cells. Which immunodeficiency best explains these findings?

• A X-linked agammaglobulinemia
• B Selective IgA deficiency
• C Hyper-IgM syndrome
• D Common variable immunodeficiency ✓

Explanation

Common variable immunodeficiency (CVID) presents after childhood with low IgG, IgA, and IgM, normal B-cell numbers, and failure of B cells to differentiate into plasma cells. X-linked agammaglobulinemia has absent B cells. Selective IgA deficiency shows only low IgA with normal IgG and IgM. Hyper-IgM syndrome has normal or elevated IgM with low IgG and IgA due to defective class switching.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.