Diagnostic Pitfalls of a Newborn with Congenital Nephrogenic Diabetes Insipidus

Congenital nephrogenic diabetes insipidus (NDI) is a rare cause of hypernatremia in newborns. Central diabetes insipidus (CDI) is the main differential diagnosis in NDI, however NDI responds poorly to desmopressin acetate (DDAVP) treatment, while this is the mainstay of CDI management. Therefore, early and correct diagnosis of NDI is important to avoid the complications of inappropriate therapy. We report a newborn with hypernatremia and hypotonic polyuria. The patient was initially responsive but subsequently unresponsive to intranasal DDAVP treatment in terms of both urine output and serum sodium levels. A novel hemizygous missense mutation (c.632T>C, p.L211P) in the AVPR2 gene was found in both the baby and his mother, and the diagnosis of congenital NDI was established. After hydrochlorothiazide treatment and hypo-osmolar formula were given, urine volume was decreased, and serum sodium levels were normalized. Early recognition and appropriate management of NDI may prevent complications of hypernatremic dehydration in young infants.