Bone oxalosis and renal osteodystrophy

Bone biopsy specimens from four patients with hyperoxaluria who underwent hemodialysis were studied. Calcium oxalate crystals are laid down in marrow spaces and sometimes inside the bone matrix and uncalcified osteoid tissue. They are clearly visible by polarizing microscope and are stained grayish-brown by Pizzolato's method. Most are surrounded by basophilic, amorphous material. By electron microscope they appear as elongated, empty spaces and after hydrogen peroxide treatment appear as fragmented, slightly electron-dense, needle-like structures. In marrow spaces, oxalate crystals aggregate in round clusters surrounded by a granulomatous reaction. This, however, cannot remove the oxalate crystals. Bone histology shows advanced renal osteodystrophy, ie, severe osteomalacia and hyperparathyroidism. The granulomatous reaction induced by the oxalate crystals probably contributes to and worsens the changes from hyperparathyroidism.