Two types of nutritional rickets in infants.

In 100 infants with nutritional rickets, i.e., responsive to vitamin D therapy, we found a close inverse relationship between serum phosphorus, on the one hand, and serum alkaline phosphatase and the presence of radiological signs of rickets, on the other. There was no correlation between serum calcium and the severity of bone lesions. It is concluded that hypophosphatemia but not hypocalcemia is typical of rickets. Since hypophosphatemia and rickets can be produced experimentally by phosphate deficiency alone, we suggest our infants can be divided into two groups, one with true vitamin D deficiency that leads to hypocalcemia and no or mild bone lesions, and one with primary phosphate deficiency, resulting perhaps from a defect in phosphate transport, which leads to rickets and hypophosphatemia.