DiGeorge syndrome results from a 22q11.2 deletion affecting pharyngeal pouch development. The primary immunological defect is:
- A T-cell deficiency due to thymic aplasia/hypoplasia — absent thymic shadow on chest X-ray ✓
- B B-cell deficiency with absent immunoglobulins — panhypogammaglobulinaemia from birth
- C NK-cell deficiency with susceptibility to viral infections and haemophagocytosis
- D Neutropenia with recurrent pyogenic infections and absent lymph nodes
Correct answer: A. T-cell deficiency due to thymic aplasia/hypoplasia — absent thymic shadow on chest X-ray
Explanation
DiGeorge syndrome (22q11.2 deletion / velocardiofacial syndrome) involves defective development of the 3rd and 4th pharyngeal pouches, which give rise to the thymus and parathyroid glands. Thymic aplasia or hypoplasia leads to profound T-cell deficiency with susceptibility to viral and fungal infections, while B cells are relatively preserved (though T-cell help is impaired). Associated features include conotruncal cardiac defects, hypocalcaemia, and facial dysmorphisms.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.