Idiopathic infantile hypercalcemia: case report and review of the literature.

The widespread use of supplemental vitamin D has dramatically reduced the incidence of rickets. While generally considered a safe practice, there is potential for toxicity in patients with idiopathic infantile hypercalcemia (IIH). Inadequate 24-hydroxylase-enzyme activity renders these individuals unable to degrade active vitamin D, resulting in hypercalcemia due to increased intestinal calcium absorption, decreased renal calcium excretion, and increased osteoclastic bone activity. Clinicians should be aware that even therapeutic doses of vitamin D can prove harmful for patients with CYP24A1 mutations. Studies have also demonstrated a link between inadequate 24-hydroxylase activity and nephrocalcinosis, renal insufficiency, and calcium containing kidney stones, further emphasizing the importance of early recognition of this disease and judicious use of vitamin D. We present a case with an interesting diagnostic algorithm used to diagnose IIH when given an incomplete history and subsequently review the existing literature on the subject.