An unusual form of vitamin D-dependent rickets in a child: alopecia and marked end-organ hyposensitivity to biologically active vitamin D.

A 12-yr-old female patient with an unusual form of vitamin D dependency and alopecia is described. She was a product of consanguineous mating and developed signs and symptoms suggesting vitamin D dependency early in life. Neither 150 microgram/day (6 microgram/kg.day) 1 alpha-hydroxyvitamin D3 nor 5 microgram/day (0.2 microgram/kg.day) 1,25-dihydroxyvitamin D3 proved to have an effect on her abnormal serum chemistry. Seven million international units per day (about 2 x 10(5) IU/kg.day) of native vitamin D restored her serum chemistry to normal and brought about marked improvement on skeletal radiographs, when her serum 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, and 24,25-di-hydroxyvitamin D were 4250, 4.8, and 35 ng/ml, respectively. Even with the high serum levels of vitamin D metabolites, her intestinal 47Ca absorption rate remained in the lower normal range and urinary calcium excretion was decidedly low. Association of hypoparathyroidism was ruled out. These results suggest that the patient has extreme and-organ (intestine) hyposensitivity, probably of congenital origin, to the biologically active metabolites of vitamin D.