A patient with congenital nephrogenic diabetes insipidus due to AVPR2 mutation complicated by persisting polydipsia under hemodialysis treatment.

A 17-year-old boy was referred to our institution for a re-evaluation of congenital nephrogenic diabetes insipidus. A water restriction test revealed no urine concentration or volume reduction and a subsequent pitressin test revealed a lack of an anti-diuretic response. Nephrogenic diabetes insipidus was confirmed, and the patient was treated using trichlormethiazide 4 mg, indomethacin 175 mg, and desmopressin 20 μg. His blood pressure and weight were not controlled owing to polydipsia and polyuria secondary to acquired excessive water drinking behavior. Repeated admissions for weight control were necessary and despite consultation with a psychiatrist for his obsessive water drinking behavior, he had end-stage renal failure after 30 years of treatment. Genetic testing revealed AVPR2 mutation (c. T866C: p. L289P) that had previously been reported as a pathogenic mutation. His excessive drinking behavior persisted, leading to hyponatremia even after initiation of hemodialysis. There was also difficulty in achieving body weight control, which was managed by repeated admissions with restriction of water intake, being the mainstay of management.