Unveiling <i>CYP24A1</i> Mutation in Unexplained Hypercalcemia in an Adult: A Case Report

We present the clinical history of a 60-year-old man with persistent skeletal pain and recurrent renal stones associated to chronic hypercalcemia with fluctuating serum calcium levels. Elevated 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D concentrations in the absence of vitamin D supplementation together with a decreased 24,25-dihydroxyvitamin D concentration suggested altered vitamin D metabolism. Genetic testing demonstrated a biallelic loss-of-function mutation in the CYP24A1 gene, responsible for reduced vitamin D inactivation. This rare condition, usually associated with idiopathic infantile hypercalcemia, may manifest later in life. Early recognition and management are critical to prevent complications such as recurrent nephrolithiasis, nephrocalcinosis, and renal failure.