Pathogenesis of Hereditary Vitamin-D-Dependent Rickets

Abstract

Requirements of vitamin D₂, vitamin D₃, 25-hydroxyvitamin D₃ and 1α,25-dihydroxyvitamin D₃ were studied in five patients with vitamin-D-dependent rickets, a recessively inherited form of vitamin-D-refractory rickets. Massive doses of vitamin D₂ (1.25 to 2.50 mg per day), vitamin D₃ (1.25 mg per day) and 25-hydroxyvitamin D₃ (0.4 to 0.9 mg per day) were required to heal the rachitic lesions, but minute doses of 1α,25-dihydroxyvitamin D₃. (1.0 μg per day) promptly initiated healing. The dosage of 1α,25-dihydroxyvitamin D₃ was probably in the physiologic range for the human infant — evidence against target-cell unresponsiveness.