Treatment of vitamin D resistant hypophosphataemic osteomalacia with 1alpha-hydroxy vitamin D3
Peacock, M.; Heyburn, P.J.; Aaron, J.E.
Calcified Tissue Research 22(Suppl): 55-62
1977
ISSN/ISBN: 0008-0594 PMID: 912585 Document Number: 122664
Of 10 patients 10 to 80 years old with hypophosphataemic osteomalacia 2 were given up to 6 mu g 1 alpha -hydroxycholecalciferol (1 alpha -HCC) daily alone, 6 with supplements of phosphorus by mouth and 2 were not treated. Treatment was for 5 to 16 months. Before treatment all had hypophosphataemia and decreased tubular reabsorption of phosphate but normal plasma calcium, parathyrin and 25-hydroxyvitamin D values. In 4 patients plasma alkaline phosphatase and fasting urinary hydroxyproline were normal. Fasting Ca in urine was low in only 3 patients and 2 had fasting hypercalciuria. Absorption of radioactive Ca and P was low in all.Within 24 h of starting 1 alpha -HCC absorption of radioactive Ca responded and increased with increasing doses. There was a corresponding but less striking increase in absorption of P. Fasting plasma phosphate increased, to normal in some patients, and in some was associated with an increase in tubular reabsorption of phosphate. In 3 plasma alkaline phosphatase increased and hydroxyproline in urine returned slowly to normal after several months of treatment; in 2 of those there was a rapid improvement in muscle function. As those values returned to normal Ca in urine increased and mild hypercalcaemia developed but was easily controlled by reducing 1 alpha -HCC to between 2 and 3 mu g daily. There was no such response in the other patients, most of whom had normal plasma alkaline phosphatase before treatment, and fasting hypercalciuria or hypercalcaemia did not develop. In the patients who had repeat bone biopsies on treatment there was good evidence of healing with an increase in calcification fronts and a decrease in osteoid surfaces, which were correlated with the increase in plasma phosphate.