FAMILIAL IDIOPATHIC HYPERPHOSPHATASIA (FIH) - RESPONSE TO LONG-TERM TREATMENT WITH PAMIDRONATE (APD)

A 5-year-old child suffering from familial idiopathic hyperphosphatasia (FIH) was treated by: (1) intravenous infusion of pamidronate (APD) (3 h) (0.75 mg/kg/day) for 5 days; and (2) oral administration of APD (8 mg/kg/day) for 1 year, in association with calcium (1 g/day) as calcium gluconate. A decrease of both serum calcium and phosphate, and a slight PTH increase were observed immediately after the IV treatment; serum alkaline phosphatase did not change, but a marked and rapid decline in the hydroxyprolinuria was observed: basal 659 +/- 207 during IV treatment 169 +/- 59 (xBAR +/- SD mg/24 h, P <0.005). At the end of one year of oral APD treatment clinical and radiological findings showed a remarkable improvement. Serum calcium, phosphate and PTH returned to the initial values. Plasma alkaline phosphatase levels showed a 70% decrease: basal 1370 IU/1, 1 year 410 IU/1 whereas the hydroxyprolinuria values were similar to those determined at the end of the intravenous treatment (212 +/-13 mg/24 h), but still significantly lower than the basal levels (P <0.01). No side-effects were observed. APD appears to be a promising treatment for patients with FIH.