DiGeorge syndrome features?

• A. Development failure of 3rd and 4th pharyngeal arches
• B. 22q11 microdeletion
• C. Both Development failure of 3rd and 4th arches and 22q11 microdeletion
• D. Trisomy 21

Answer: (C)

DiGeorge syndrome comes from a deletion on chromosome 22q11.2 that disrupts neural crest cell migration and the development of the pharyngeal arches, especially the third and fourth arches. This developmental disruption explains thymic and parathyroid aplasia (leading to T-cell deficiency and hypocalcemia) and common conotruncal heart defects, along with facial and palate anomalies. The best answer captures both the genetic cause and the embryologic consequence—that the syndrome arises from the 22q11.2 microdeletion and produces failure of those arches’ derivatives. Trisomy 21 is a different condition, and recognizing only one aspect (either the arch failure or the deletion) misses the full DiGeorge picture.