Psychogenic polydipsia associated with hyponatremia is a potentially dangerous and fatal condition observed on patients with psychiatric illness, specially schizophrenia. This results on a peripheral oedema and can lead to cerebral oedema, mental status deterioration and intracranial hypertension if not identified and treated urgently. We present a case of polydipsia as first signal of psychosis.

20-year-old man without significant past medical or psychiatric history attended to emergency service presenting exuberant lower limbs oedemas. The analytical study stated an hyponatremia and hipo-osmotic urine. A psychiatric evaluation was made after organic illness exclusion. The patient presented serious behaviour changes, delusions and eating disturbances (“eat raw meat to recover the red cells that they had stolen from him”), polydipsia and auditory hallucinations with 2 weeks of evolution. The patient was compulsory hospitalized, treated with risperidone and lorazepam and discharged 28 days after admission without psychotic symptoms.

The recognition and management of the polydipsia as a first signal of psychosis are difficult because sometimes patients are uncooperative and tend to hide their water intake, but is important to be awhare to this signal to prevent the morbidity and mortality associated with this disease.