Rickets in Infancy and Childhood

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Abstract
Two representatives of rickets in childhood are described. Plasma levels of 25-hydroxyvitamin D (25-OH-D), serum Ca and serum P were measured in infantile rickets. Mean plasma level of 25-OH-D in rickets group was 13.1 .+-. 5.7 (SD) ng/ml (36) which was not significantly lower than that in controls. In rickets group, serum Ca and P were within normal limits though serum alkaline phosphatase increased significantly. Rickets in low birth weight infants is not absolutely due to vitamin D deficiency. The increase of requirement for vitamin D in low birth weight infants resulted in relative vitamin D deficiency. Clinical effects of massive doses of 1.alpha.-hydroxyvitamin D3 (l.alpha.-OH-D3) in patients with hypophosphatemic vitamin D resistant rickets (HVDRR) were shown. Plasma level of 1,25-(OH)2-D in 1 patient increased from 22.5 to 80.4 pg/ml 2 mo. after administration of 5 .mu.g/day of l.alpha.-OH-D3. Plasma level of 1,25-(OH)2 in another patient was 96 pg/ml 3 mo. after therapy with l.alpha.-OH-D3 at the dose level of 24 .mu.g/day. Plasma level of 1,25-(OH)2-D in a 3rd patient was 60 pg/ml 2 mo. after therapy at dose level of 16 .mu.g/day. Plasma levels of 1,25-(OH)2-D were relatively low in these patients even after administration of massive doses of l.alpha.-OH-D3. The metabolism of 1,25-(OH)2-D is accelerated in patients with HVDRR. In 2 patients there was a rise in fasting serum phosphate associated with an increase in tubular reabsorption of phosphate.