In DiGeorge syndrome, which electrolyte abnormality is typically present due to parathyroid aplasia?

• A. Hypocalcemia
• B. Hyperkalemia
• C. Hypercalcemia
• D. Hypokalemia

Answer: (A)

Parathyroid hormone is the main regulator of serum calcium. In DiGeorge syndrome, failure of development of the parathyroids (parathyroid aplasia) leads to severe PTH deficiency. Without PTH, the body can’t efficiently mobilize calcium from bone, reabsorb calcium in the kidneys, or activate vitamin D to boost intestinal calcium absorption. The net result is low serum calcium, i.e., hypocalcemia, which can cause neuromuscular irritability, tetany, or even seizures in neonates. Hyperkalemia, hypokalemia, and hypercalcemia are not characteristic of parathyroid absence; the typical disturbance here is low calcium due to lack of PTH.