[Novel mutations in the calcium-sensing receptor encoding genes as a cause of familial hypocalciuric hypercalcemia].

Hypercalcemia is a rare reason for consultation in clinical practice and is often an incidental finding in a routine biochemical evaluation. Its most frequent cause is primary hyperparathyroidism. Rarely, hypercalcemia is due to mutations in the calcium-sensing receptor (CaSR) signaling pathway that give rise to the different forms of familial hypocalciuric hypercalcemia (FHH). Two aspects are essential to suspect a probable FHH, the first is the existence of other cases in the family of elevated calcium and PTH associated with low urinary calcium excretion. In this context, a calcium clearance to creatinine clearance ratio (Ca urine 24 h. x serum Cr) / (Cr urine 24 h x serum Ca) ≤ 0.01 is highly suggestive of the diagnosis of FHH, which should subsequently be confirmed by sequencing of the genes involved in the different forms of FHH. Two families with FHH with mutations not described in the literature are presented.