DiGeorge syndrome in the context of hypoparathyroidism is best described as which of the following?

• A. Congenital dysgenesis of thymus and parathyroids
• B. Autoimmune destruction of parathyroids
• C. Hyperplasia of parathyroids
• D. Vitamin D deficiency

Answer: (A)

DiGeorge syndrome reflects a developmental failure of the third and fourth pharyngeal pouches, leading to congenital dysgenesis (or aplasia) of the thymus and parathyroid glands. This explains the association with hypoparathyroidism and hypocalcemia, since the parathyroids are absent or underdeveloped. The thymic defect also causes T-cell deficiency, contributing to immune problems.

This pattern is different from autoimmune destruction of the parathyroids, which is an acquired process and not typical of this congenital syndrome. Parathyroid hyperplasia would imply increased, not absent, parathyroid tissue and is seen in other contexts like secondary hyperparathyroidism. Vitamin D deficiency can cause low calcium but does not involve congenital absence or hypoplasia of the parathyroids, and PTH behavior differs.