Early biochemical findings in familial hypophosphataemic, hyperphosphaturic rickets and response to treatment.

Regular biochemical measurements were made in 4 babies, each of whom had one parent with familial hypophosphataemic, hyperphosphaturic rickets. Hypophosphataemia developed by 2 months and levels of alkaline phosphatase had increased by 3 months in all four. Decreased tubular reabsorption of phosphate and x-ray changes of rickets did not develop until 6 months in 3 of the babies. In the fourth these abnormalities developed at 9 days and 3 months. The babies were treated with oral phosphate and small doses of 1-alpha-hydroxy-cholecalciferol. The rickets healed readily in 3 babies and their linear growth kis within the normal range. Healing took much longer in the remaining child and his linear growth is below the 3rd centile. Hypercalcaemia has not been a problem of treatment.