Growth failure in an infant with congenital nephrogenic diabetes insipidus during sodium restriction

Congenital nephrogenic diabetes insipidus (CNDI) is an inherited disorder characterized by renal tubular insensitivity to antidiuretic hormone, resulting in an inability to concentrate urine. We report on an infant boy with CNDI who showed growth failure during treatment with sodium restriction. At the age of 4 mo, he was diagnosed as having CNDI, judging from fever with hypernatremia (serum Na 153 mEq/L), diluted urine (urine osmolarity 193 mOsm/kg), high antidiuretic hormone (plasma antidiuretic hormone 53 pg/mL), and normal renal function (serum creatinine 0.3 mg/dL). His length and weight were mean +0.4 and -1.1 SD, respectively, at that time. He was treated with sodium restriction (sodium intake; 0.53 mEq/kg/day) using low sodium formula in addition to trichlormethiazide, spironolactone, and mefenamic acid. Growth failure developed: his length and weight were mean -2.4 and -3.3 SD, respectively, at the age of 10 mo. After withdrawal of sodium restriction to 1.5 mEq/kg/day of sodium intake without any change of caloric intake and medication, catch-up growth was observed. At the age of 39 mo, the patient's height and weight were mean -0.8 and -0.6 SD, respectively. We conclude that excessive sodium restriction can cause growth failure in infants with CNDI.