DiGeorge syndrome results from failure of development of the third and fourth pharyngeal pouches, causing thymic aplasia. The predominant immunological defect is:

• A Absent B cells with severe hypogammaglobulinemia
• B Combined T and B cell deficiency with absent lymph nodes
• C Absent natural killer cells with normal T and B cell counts
• D Absent T cells with preserved B cells and normal or elevated immunoglobulins ✓

Explanation

DiGeorge syndrome (22q11.2 deletion) causes thymic aplasia so T-cell maturation cannot occur; peripheral T cells are absent or severely reduced while B cells are present (no thymus is needed for B-cell development). Without T-cell help, antibody responses to T-dependent antigens are impaired despite normal B-cell numbers. Combined T and B cell deficiency characterizes SCID; Bruton agammaglobulinemia is a pure B-cell defect.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.