[Familial benign hypercalcemia revealed by renal colic]

Diagnosis of familial benign hypercalcemia can be challenged by the association with a urinary lithiasis, which, in the presence of hypercalcemia, will most frequently lead to affirm primary hyperparathyroidism.

We report the case of a 23 year-old patient who presented with a left ureteral stone composed of calcium oxalate. His serum total calcium value was 2.92 mmol/l. Serum PTH value was inappropriately in the normal range (32 ng/l, normal values 10 to 58 ng/l). Hypercalcemia persisted despite a subtotal parathyroidectomy and new investigation biochemical revealed familial benign hypercalcemia.

This diagnosis is usually made fortuitously, since most patients have few, if any, symptoms. A past familial history of hypercalcemia and several biochemical features (such as a reduced fractional excretion of calcium, mild hypermagnesemia, and a normal serum inorganic phosphorus level) are helpful dues to the diagnosis of familial benign hypercalcemia. In some cases, however, searching for an inactivating mutation of the extracellular calcium-sensing receptor gene is necessary to distinguish this autosomal dominant disease from primary hyperparathyroidism.