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Vitamin D-resistant rickets
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 and an X-linked dominant form, the latter caused by mutation in the phosphate-regulating gene with homologies to endopeptidases 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 caused by mutation in the vitamin D receptor gene on 12q. Also sometimes called vitamin D–dependent rickets type II. | |
