Vitamin D-induced hypercalcemia and nephrolithiasis in a 58-year-old woman with biochemical findings suggestive of 24-hydroxylase deficiency: a case report.

Background: Hypercalcemia is most often caused by primary hyperparathyroidism and malignancies. Non-parathyroid hormone (PTH)-dependent hypercalcemia can be caused by abnormal vitamin D metabolism related to excess production from granulomatous disease, excess intake or defects in its degradation. Disturbance in vitamin D metabolism can lead to increased vitamin D sensitivity which can cause hypervitaminosis D at doses otherwise considered safe. Decreased 24-hydroxylase activity due to Case Description: A 58-year-old woman presented with hematuria and abdominal pain secondary to nephrolithiasis. Laboratory studies revealed hypercalcemia, suppressed PTH, and markedly elevated 25-hydroxyvitamin D [25(OH)D] following standard vitamin D supplementation (2,000 international units/day). Her 1,25(OH) Conclusions: This case highlights hypercalcemia and nephrolithiasis triggered by standard-dose vitamin D supplementation in a previously asymptomatic woman with biochemical findings indicating CYP24A1 deficiency illustrating that the disorder may remain latent until challenged by exogenous or endogenous vitamin D excess. Although genetic testing remains the gold standard for diagnosis, a markedly elevated 25(OH)D:24,25(OH)