Which pharyngeal arches are linked to DiGeorge syndrome?

• A. First and Second
• B. Second and Third
• C. Third and Fourth
• D. Fourth and Fifth

Answer: (C)

DiGeorge syndrome comes from failed development of the third and fourth pharyngeal pouches during embryogenesis. The thymus and inferior parathyroids originate from the third pouch, while the superior parathyroids come from the fourth pouch. When these structures don’t form properly, you get thymic aplasia or hypoplasia (leading to deficient T-cell immunity) and hypoparathyroidism (causing low calcium). This combination, along with potential conotruncal heart defects from neural crest migration problems, is characteristic of the syndrome. So the pharyngeal-pouch pair involved is the third and fourth. Other pharyngeal derivatives from different pouches don’t account for these specific immune and parathyroid findings.