Hypophosphataemic osteomalacia presenting in adults.

Abstract

Nine patients were studied with primary hypophosphataemic osteomalacia presenting in adult life. The clinical features of this relatively homogeneous syndrome include bone pains, muscle weakness, and often marked height loss due to vertebral collapse. There is no history of rickets or other disease in childhood, and the incidence is entirely sporadic. Radiological and biochemical findings are otherwise typical of the sex-linked form of ‘vitamin D resistant’ osteomalacia, with normal plasma and urinary calcium, variably raised alkaline phosphatase, and persistent hypophosphataemia due to high renal phosphate clearance. In addition many patients exhibit increased urinary glycine excretion readily detectable on routine paper chromatography. Treatment of this condition requires oral phosphate supplements, probably for life, in addition to high doses of vitamin D. Calcium supplements are also valuable during the healing phase (approximately one year). Gastrointestinal upset, especially diarrhoea, may complicate necessary phosphate treatment. Our initial regime now includes vitamin D2 5 mg daily, dibasic sodium phosphate (Na2HPO4.10H2O) 10 g daily (or equivalent, e.g. ‘Phosphate Sandoz’), and a calcium supplement providing approximately 1000 mg daily. The maintenance dose of vitamin D is under 2 mg a day and calcium supplements may be withdrawn after approximately 1–2 years.