Acquired nonfamilial osteomalacia: Factors in pathogenesis and the results of long-term treatment with oral phosphate

Abstract

A forty year old man had extensive, severe osteomalacia, with clinical onset at age thirty-two. Clinical and chemical studies of the family were noncontributory. The distinctive findings in mineral metabolism were deficient absorption of calcium from the gastrointestinal tract (evaluated isotopically), normocalcemia, hypophosphatemia and a marked increase in the clearance of phosphate (reduced to normal by the stimulus of a calcium infusion) and increased retention of infused calcium. Urinary hydroxyproline excretion, which was increased, could also be reduced by the hypercalcemia. This sequence suggests that the cause of the hypophosphatemia was a secondary hyperparathyroidism due to the defective gastrointestinal absorption of calcium, with resultant hyperphosphaturia. Long-term treatment with oral phosphorus as the only therapy brought about clinical and chemical improvement, concomitantly with normalization of gastrointestinal absorption of calcium. Serum alkaline phosphatase and urinary hydroxyproline levels showed a gradual and parallel fall, whereas serum phosphate increased to normal values.