Nephrocalcinosis is associated with renal tubular acidosis in children with X-linked hypophosphatemia.
BACKGROUND
X-linked hypophosphatemia is characterized clinically by rickets and growth retardation. Therapy of this disorder with phosphate and vitamin D often produces nephrocalcinosis. The long-term effects of nephrocalcinosis on renal function in patients with X-linked hypophosphatemia are unknown. The purpose of this study was to evaluate the prevalence of glomerular and tubular disorders in patients with X-linked hypophosphatemia who developed nephrocalcinosis.


METHODS
The creatinine clearance and the prevalence of renal tubular acidosis were compared in 19 patients with X-linked hypophosphatemia and nephrocalcinosis with 15 patients with X-linked hypophosphatemia without nephrocalcinosis.


RESULTS
Sixteen of the 19 patients (84%) with nephrocalcinosis had a hyperchloremic metabolic acidosis compared with one of the 13 patients without nephrocalcinosis (P < .01). The serum bicarbonate of patients with nephrocalcinosis was 20.0 +/- 0.7 as compared to 24.5 +/- 0.6 mmol/L in patients without nephrocalcinosis (P < .01). The urinary anion gap was positive in all patients with acidosis (+62.1 +/- 13.3 mmol/L). The creatinine clearance was 125 +/- 6 mL/min/1.73 m2 in patients with nephrocalcinosis and 124 +/- 7 mL/min/1.73 m2 in those without nephrocalcinosis.


CONCLUSIONS
Therapy of X-linked hypophosphatemia is often associated with nephrocalcinosis. Nephrocalcinosis is associated with renal tubular acidosis in patients with X-linked hypophosphatemia.
Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas 75235-9063, USA.
M
M
Seikaly
R
R
Browne
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M
Baum
D000141:Acidosis, Renal Tubular / Q000209:etiology*; D000293:Adolescent; D000328:Adult; D001639:Bicarbonates / Q000097:blood; D002648:Child; D002675:Child, Preschool; D003404:Creatinine / Q000097:blood; D006801:Humans; D007015:Hypophosphatemia, Familial / Q000150:complications / Q000188:drug therapy*; D009397:Nephrocalcinosis / Q000097:blood / Q000139:chemically induced* / Q000150:complications; D010710:Phosphates / Q000009:adverse effects*; D015995:Prevalence; D012189:Retrospective Studies; D014807:Vitamin D / Q000009:adverse effects*
D001639:Bicarbonates; D010710:Phosphates; D014807:Vitamin D; D003404:Creatinine