Mutations in CYP24A1 and Idiopathic Infantile Hypercalcemia

Mutations in a vitamin D–metabolizing enzyme were found in patients with idiopathic infantile hypercalcemia. The mutations may explain the patients' vitamin D sensitivity and may be a genetic risk factor for symptomatic hypercalcemia in otherwise healthy infants given vitamin D. Vitamin D plays a central role in calcium homeostasis and bone metabolism. 1 Vitamin D supplementation or food fortification for the prevention of rickets is advocated routinely for all infants. Although vitamin D is potentially dangerous in very high doses, the margin of safety between the daily requirements of vitamin D and levels that produce toxic effects is considered to be quite large. 2 However, in the early 1950s, there were reports about a number of infants with unexplained hypercalcemia who presented with failure to thrive, vomiting, dehydration, spikes of fever, and nephrocalcinosis. 3 , 4 Laboratory evaluation of these infants revealed severe hypercalcemia . . .