In common variable immunodeficiency (CVID), the most characteristic immunological defect is:

• A Absent B cells in peripheral blood with markedly reduced immunoglobulins due to early pro-B cell differentiation arrest
• B Profound reduction of all serum immunoglobulin classes (IgG, IgA, IgM) with impaired specific antibody response to vaccination, despite normal B-cell numbers, due to defective B-cell differentiation to plasma cells ✓
• C Isolated IgA deficiency with normal IgG and IgM, presenting with recurrent sinopulmonary infections
• D Marked reduction of CD4+ T cells with secondary hypogammaglobulinemia due to absent T-cell help

Explanation

CVID is the most common symptomatic primary immunodeficiency in adults. It is characterized by low serum immunoglobulins (all classes, especially IgG), failure to produce specific antibodies following vaccination, and recurrent sinopulmonary bacterial infections. Unlike X-linked agammaglobulinemia (XLA), CVID patients have normal or near-normal numbers of circulating B cells that are unable to differentiate into immunoglobulin-secreting plasma cells due to heterogeneous defects in B-cell signaling and maturation. XLA shows absent B cells with Bruton tyrosine kinase (BTK) mutations. Isolated IgA deficiency is the most common primary antibody deficiency but is usually asymptomatic. HIV-related hypogammaglobulinemia is secondary to CD4 depletion.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.