A Familial Syndrome of Hypocalcemia with Hypercalciuria Due to Mutations in the Calcium-Sensing Receptor

Hypocalcemia is the hallmark of hypoparathyroidism, which may be inherited either as an isolated endocrinopathy or as part of an autoimmune polyendocrinopathy–candidiasis–ectodermal dystrophy or the DiGeorge syndrome, in which developmental defects of the third and fourth pharyngeal pouches result in parathyroid and thymic aplasia together with cardiac and facial abnormalities. 1 – 3 Genetic studies have mapped the autoimmune polyendocrinopathy–candidiasis–ectodermal dystrophy syndrome and the DiGeorge syndrome loci to chromosomes 21q22.3 2 and 22q11, 3 respectively, and studies of families with isolated hypoparathyroidism have mapped an X-linked recessive form to chromosome Xq26–q27. 4 In two kindreds with autosomal hypoparathyroidism, mutations of the parathyroid hormone gene, located . . .