Heterozygous and homozygous CASR mutations that inactivate CASR are responsible, respectively, for familial hypocalciuric hypercalcemia, type 1 (also known as familial benign hypercalcemia) (OMIM #145980) [12]–[13] and neonatal severe hyperparathyroidism (OMIM #239200) [13]. The gene discussed is CASR; the disease is familial hypocalciuric hypercalcemia.