The case of an 8 year old boy with both nocturnal enuresis andnephrogenic diabetes insipidus is presented. Diagnosis of nephrogenic diabetes insipidus was based on a typical medical history, the characteristic result of a fluid restriction test, the lack of aneffect of 1-desamino-8-D-arginine (DDAVP) on both urineosmolality and plasma coagulation factors and, finally, the detectionof a hemizygous missense mutation within the arginine vasopressin (AVP) receptor gene. Hydrochlorothiazide treatment and dietary measuresreduced the patient's urine volume to one third of its originalvolume. However, this had no effect on enuresis. The daily intranasalapplication of DDAVP did not further reduce urine output butdramatically decreased the frequency of bed wetting. This observationcontradicts the common notion that the therapeutic effect of DDAVP innocturnal enuresis is the result of compensation for a nocturnal AVPdeficit. Rather, it points to a different mode of action of DDAVP inpatients with enuresis. It is hypothesised that central AVP receptorsare a target of DDAVP and that they might play an important role in thepathogenesis of nocturnal enuresis.
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