Vitamin-D-Resistant Osteomalacia in Hemodialysis Patients Lacking Secondary Hyperparathyroidism

Abstract

A sporadic, vitamin-D-resistant osteomalacic syndrome is described in 19 patients undergoing hemodialysis. The syndrome was found in < 1.5% of patients from referring dialysis centers. All 19 patients had multiple fractures, severe myopathy, and many developed spontaneous hypercalcemia. Severe osteomalacia without evidence of secondary hyperparathyroidism distinguished this syndrome from other forms of renal osteodystrophy. Bone Al, measured in 6 patients, was greatly elevated. Therapy with calcitriol (1.alpha.,25-dihydroxycholecalciferol) led to clinical improvement in 7 patients with reduced pain and myopathy, decreased serum alkaline phosphatase, or both, but no improvement in bone histology. Patients who did not respond clinically to calcitriol developed marked hypercalcemia. The cause of this severe osteomalacia, which occurs despite normal or slightly elevated levels of serum Ca and P and fails to mineralize with calcitriol, is unclear.