Nephrogenic diabetes insipidus – case report of a family from Romania

Introduction: Nephrogenic diabetes insipidus is a rare X linked syndrome, secondary to mutations in the gene encoding the vasopressin V2 receptor, located at position Xq28. Aim: To present a family with nephrogenic diabetes affecting three males in two generations. Material and method: We report the cases of a 4 month old patient, male, admitted in our hospital for growth impairment, vomiting and fever, and his 10 year old uncle, admitted at the same time for excessive fluid intake (11 liter/day). Results: Family history (two generations affected; uncle’s brother died at the age of two with severe hypernatremic dehydration), polyuria 7.8 ml/kg/h, lab work-up (plasma hyperosmolarity, hypernatremic hyperchloremic alkalosis, extremely low urine density (1002), elevated ADH levels) were suggestive for nephrogenic diabetes insipidus. Treatment with hydrochlorothiazide was initiated (2mg/kg/body), with reduction in urine output (2.85 ml/kg/h), but severe consecutive alkalosis and hypokalemia in the infant. An aldosterone antagonist (spironolactone) was added, with good response. Uncle’s fluid intake was reduced to 3-4 l/day, while urine output decreased to 3 l/day. Discussion: Diabetes Insipidus includes a large series of disorders. Many of the known disorders are now susceptible to symptomatic treatments or specific interventions such as dietary modification, thiazides and inhibitors of prostaglandin synthesis. However, these approaches can only ameliorate the clinical phenotype. In infants, treatment is particularly difficult. It aims to avoid episodes of dehydration and obtain a normal growth curve. Conclusions: This highlights the importance of early diagnosis of diabetes insipidus in infants with persistent hypernatremia.