Primary bone oxalosis: the roles of oxalate deposits and renal osteodystrophy.

Primary oxalosis is a rare congenital disorder. The excessive oxalate biosynthesis induces deposits in many organs, particularly in kidney and bone. The late onset of primary oxalosis is reported in a 50-year-old man. His chronic renal failure was treated by maintenance hemodialysis for 3 years. He then developed a diffuse bone disease with osteosclerosis and roentgenographic features of hyperparathyroidism. A parathyroidectomy was performed, with debatable improvement of bone lesions. Laboratory results and histologic and histomorphometric studies before and after parathyroidectomy suggest a double histopathogenetic mechanism for this bone disease: renal osteodystrophy and massive bone oxalate deposits. Such deposits may induce both a heterogeneous osteosclerosis with dense metaphyseal bands and histologic bone lesions similar to those of hyperparathyroidism. The crystalline deposits induce in the bone tissue a granulomatous macrophagic reaction. These macrophages are unable to phagocytize the crystals and may be involved in active bone resorption. Bone lesions of oxalosis occur in patients with chronic renal failure, and hyperparathyroidism has a worsening role.