vitamin D-resistant rickets
Definition: a group of metabolic disorders characterized by renal tubular defects in phosphate transport and bone abnormalities resulting in hypophosphatemic rickets or osteomalacia; hypocalcemia and tetany are not features. There is an autosomal dominant form [MIM*193100] and an X-linked dominant form [MIM*307800], the latter caused by mutation in the phosphate-regulating gene with homologies to endopeptidases (PHEX) on chromosome Xp. Both forms are not responsive to standard therapeutic doses of vitamin D but they may respond to very large doses of phosphate and/or vitamin D. There is also an autosomal recessive form [MIM*277440] caused by mutation in the vitamin D receptor gene (VDR) on 12q. Also sometimes called vitamin D–dependent rickets type II.
Synonym(s): familial hypophosphatemic rickets