Hypercalcaemia complicating systemic oxalosis in primary hyperoxaluria type 1

Persistent hypercalcaemia was observed in two patients with oxalate osteopathy complicating primary hyperoxaluria type 1; four other cases have been reported in the literature. In none of the six patients could hypercalcaemia be ascribed to hyper-parathyroidism secondary to renal failure. It occurred in the absence of aluminum intoxication, and was associated with normal calcitriol. Hypercalcaemia responded to mithramycin in one patient, and to corticosteroid administration in three; corticosteroid withdrawal was followed by recurrence of hypercalcaemia in the three cases. It is suggested that hypercalcaemia results from the osteoclast-stimulating activity of macrophages constituting the granulomata which invade the bone marrow in response to oxalate deposition. Whatever its pathogenesis, a trial of corticosteroid appears warranted for treating hypercalcaemia complicating oxalosis.