[Congenital nephrogenic diabetes insipidus: a difficult diagnosis?].

In five patients (a boy aged 10 years, a boy aged 3 months, his brother aged 1 week, the brother of the mother of the last-mentioned two boys who had died at the age of one, and a girl of kindergarten age) congenital nephrogenic diabetes insipidus was diagnosed. This rare syndrome (prevalence 1:500,000) is caused by renal insensitivity to the antidiuretic hormone arginine vasopressin. In infancy the symptoms of this disorder are aspecific, and the main symptoms of the disease, polyuria and polydipsia, often remain unnoticed at this young age. A simple anamnesis and a few laboratory tests should suggest the diagnosis. Early diagnosis and genetic counselling are possible as the molecular effects involved have been elucidated.