NEPHROGENIC DIABETES INSIPIDUS WITH A V2 RECEPTOR MUTATION AT A FUNCTIONALLY CRITICAL SITE

We present an infant with congenital nephrogenic diabetes insipidus with a V2 receptor mutation. The infant was admitted to our hospital because of high fever 7 days after birth. Laboratory examinations demonstrated elevated serum sodium (152 mEq/L) and chloride (113mEq/L) concentrations. Plasma osmolarity was increased to 312 mOsm/kg, even though urinary osmolarity was 76 mOsm/kg. Serum AVP concentration was markedly increased. Pitressin-loading test did not show marked increment in the urinary osmolarity or secretion of urinary cyclic-AMP. Therefore, the patient was clinically diagnosed as having nephrogenic diabetes insipidus. DNA analysis of the V2 receptor gene identified a C to A transition at nucleotide position 1503. This mutation leads to a predictable change from Proline to Histidine. The patient was fed a sodium-restricted formula and administered trichlormethiazide. After initiating treatment, the serum concentration of Na was maintained below 150 mEq/L, and there was no physical dysfunction or mental retardation. Early diagnosis followed by early interventions was important to improve the prognosis