Psychogenic polydipsia has an estimated prevalence of 6–20% in psychiatric population. Although first described in the 1930s, there are few studies addressing this problem and its management. The high water intake can lead to severe hyponatremia with a mortality rate high enough to merit clinical concern.

Report a case of a schizophrenic patient with psychogenic polydipsia and hyponatremia.

Retrospective review of the clinical file and literature research on this topic.

A 41-year-old man with a long-term schizophrenia presented to the emergency room (ER) with exacerbation of psychotic symptoms. In the prior 24months, he had stopped medication and began excessive water intake (5 to 10L/day). He presented with auditory hallucinations, passivity phenomena and persecutory and other delusional thoughts that justified this behavior – “The water will end; I have to stock it, like camels do”. Presently he had an asymptomatic hyponatremia (128mg/dL), but 6months before he had been admitted in the ER with vomiting, altered state of consciousness and convulsions secondary to severe hyponatremia (108mg/dL). During the present hospitalization, organic causes of hyponatremia were excluded and he was started on behavioral measures and antipsychotics. The psychotic symptoms improved and there was no need for water restriction after the first week, with restored natremia values on discharge.

With this case report we intended to raise awareness on this potentially fatal condition that despite its prevalence has no defined diagnostic criteria, nor established controlled trials concerning the effectiveness of treatments.