Thiazide diuretics arrest the progression of nephrocalcinosis in children with X-linked hypophosphatemia.

OBJECTIVE X-linked hypophosphatemia (XLH) is characterized clinically by rickets, hypophosphatemia, and hyperphosphaturia. Conventional treatment of XLH with oral phosphate and vitamin D is associated with increased urinary calcium excretion and nephrocalcinosis. Thiazide diuretics decrease urinary calcium excretion. The objective of this study was to determine the effect of thiazide diuretics on the clinical and radiologic course of nephrocalcinosis in children with XLH. METHODS The effect of hydrochlorothiazide (HCTZ) on clinical and radiologic progression of nephrocalcinosis was evaluated in 11 children with XLH. All patients had been treated previously with vitamin D and oral phosphate and had radiologic evidence of nephrocalcinosis. The average age of the patients at the start of HCTZ was 6.6 +/- 1.0 years. The effect of oral HCTZ at 0.8 +/- 0.1 mg/kg body weight per day given for 3.3 +/- 0.6 years on the progression of nephrocalcinosis and urinary calcium excretion was evaluated. RESULTS There was no change in serum phosphorous, calcium, potassium, and chloride after HCTZ therapy. HCTZ therapy increased serum bicarbonate and decreased urinary calcium excretion. The grade of nephrocalcinosis increased from 0.4 +/- 0.2 to 1.5 +/- 0.3 in the 2.3 +/- 0.3 years before initiation of HCTZ therapy, whereas the degree of nephrocalcinosis was stable after 3.3 +/- 0.6 years of HCTZ therapy (1.5 +/- 0.3 vs 3.0 +/- 0.3). CONCLUSION HCTZ decreased urinary calcium excretion but did not result in the resolution of nephrocalcinosis. However, when compared with the control period, HCTZ prevented the progression of nephrocalcinosis in children with XLH.