Familial hypocalciuric hypercalcemia
(FHH) is a benign, inherited condition that causes abnormally high levels of calcium in the blood (hypercalcemia). Affected individuals usually do not have any signs or symptoms of the condition, and hypercalcemia is often diagnosed incidentally. In some individuals, weakness, fatigue, thought disturbance, and/or excessive thirst (polydipsia) have been reported. FHH is usually caused by mutations in the CASR gene, although abnormalities in other, unidentified genes have been documented. It is inherited in an autosomal dominant manner. Treatment is typically considered unnecessary because it is a benign condition. FHH can be difficult to distinguish from primary hyperparathyroidism, for which parathyroidectomy is typically performed; individuals with FHH are typically advised to avoid parathyroidectomy. Source: Genetic and Rare Diseases Information Center (GARD), supported by ORDR-NCATS and NHGRI.