Hereditary nephrogenic diabetes insipidus is a rare disease. We describe here three brothers with this disease from a big family consisting of 10 siblings. The case is undoubtedly X-linked because the sufferers are only boys, one of them with a different father. The illness was noticed rather late, namely, at the ages of approximately 7, 6 and 5 years. Possibly, this is a particular characteristic of this family, because the disease is usually diagnosed before the age of two years. In the oldest brother (at present 15 years old) epicystotomy was performed at the time of diagnosis because of polyuria, hydroureteronephrosis and bladder hypotonia; the intervention caused a urinary tract infection leading to chronic pyelonephritis and renal scarring. No urologic intervention was necessary in the younger brothers, because their illness was noticed and treatment started somewhat earlier. This case shows that polydipsia and polyuria should always be assessed properly to disclose their causes.
Adolescent Child