Which pharyngeal arches are involved in DiGeorge syndrome according to the material?

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

Answer: (C)

DiGeorge syndrome arises when the developing pharyngeal pouches fail to form properly, especially those that become the third and fourth pouches. The third pouch gives rise to the thymus and the inferior parathyroids, while the fourth pouch contributes to the superior parathyroids and other structures. When these pouches don’t develop correctly, you get thymic aplasia (or hypoplasia) and parathyroid hypoplasia, which explains immunodeficiency and hypocalcemia often seen in this condition, along with characteristic heart defects from related neural crest issues. Since the first and second pouches aren’t the sources of thymic or parathyroid tissue, they’re not implicated here, and the classic association is with the third and fourth pouches.