A CYP24A1 Gene Mutation: A Rare Cause of Adult Onset Recurrent Nephrolithiasis

ABSTRACT CYP24A1 homozygous gene mutation is a well-known cause of infantile hypercalcemia and adult onset hypercalcemia/nephrocalcinosis. A mutation in this gene causes the loss of function of 24 hydroxylase enzyme that is essential for the catabolism of vitamin D metabolites. We describe a rare case of a 35 -year-old man with recurrent nephrolithiasis carrying two heterozygous variants of the CYP24A1 gene. He had recurrent nephrolithiasis as adult without hypercalcemia as child. He has strong family history of kidney stones. Biochemical work up showed hypercalcemia, hypercalciuria, high 1,25-dihydroxyvitamin D and low parathyroid hormone level. Hypercalciuria and recurrent nephrolithiasis resolved with thiazide diuretic without worsening in serum hypercalcemia.  CYP24A1 inactivation mutations should be suspected in adults with personal and family history of recurrent nephrolithiasis if they present with non PTH-mediated hypercalcemia and/or hypercalciuria and elevated 1,25-dihydroxyvitamin D level even without a history of hypercalcemia during childhood. Thiazide diuretic may be used for its management safely.