Familial hypocalciuric hypercalcemia revealed by chondrocalcinosis

Calcium pyrophosphate dihydrate crystal deposition disease (CPPD-CDD) has been associated to hypercalcemia. Familial hypocalciuric hypercalcemia (FHH) is a rare but important consideration in the differential diagnosis of hypercalcemia. This autosomal dominantly inherited condition is characterized by elevated plasma calcium levels, relative or absolute hypocalciuria, and normal to moderately elevated plasma PTH level. The disease is caused by inactivating mutations in the calcium-sensing receptor gene.

We describe a 77-year-old Italian man with arthritis secondary to CPPD-CDD and hypercalcemia. Clinical and biochemical data (s-Ca: 2.94 mmol/L; PTH: 5.9 pmol/L; 24 h urinary calcium: 69.6 mg; calcium/creatinine clearance: 0.004) suggested the diagnosis of FHH. Mild hypocalciuric hypercalcemia was also found in five of seven relatives confirming the diagnosis, of these one showed chondrocalcinosis.

It is important to screen for FHH using fractional urinary excretion of calcium in subjects with CPPD-CDD associated to hypercalcemia, this approach may prevent unnecessary parathyroidectomy.