A family case of nephrogenic diabetes insipidus

Two brothers, patient 1 with fever and vomiting, and patient 2 with failure to gain weight were studied. After 4 hr of water deprivation test, the urinary osmolality of the patient 1 was only 105 mOsm/liter and his body weight showed a 4.6% reduction. In response to desamino-8-D arginine vasopressin intranasal administration, no significant elevation of urinary osmolality of patient 1 occurred. After low dose vasopressin tests, the maximal urinary osmolality of their father was in the normal range, but that of their mother was below the normal range. Moreover, the patients showed no significant increase of urinary osmolality after the same tests. The brothers were diagnosed as nephrogenic diabetes insipidus (NDI) and their mother was diagnosed as a carrier. An early diagnosis of NDI is important, since adequate managements such as low-solute diet with restricted protein and salt intake or such as water intake at frequent intervals can prevent the hyperosmolality which would develop the delayed mental and physical developments. The usefulness of the combination of indomethacin with thiazide diuretics is described.