To investigate the diagnostic features of polydipsia, intermittent hyponatremia and psychosis syndrome(PIP).

The clinical data of a PIP patient admitted to the Department of Internal Medicine of Linyi Municipal Mental Health Center On February 1, 2021 was retrospectively evaluated and studied.

The 44-year-old man endured 29 years of schizophrenia. He started experiencing polydipsia in 2011 and began to drink a lot of water, up to 30 000 ml a day over the past two years. He had urine incontinence, glazed eyes, being unresponsive to calls, and slurred speech after drinking a large amount of water on the day of admission. At the time of admission, the patient′s consciousness was blurry and his blood pressure was 158/102 mmHg(1 mmHg=0.133 kPa). The muscles in the limbs were tense, making it difficult to coordinate the testing of muscle strength. The pathogenic reflex was not elicitable, but the physiological reflex was evident. Serum potassium was 3.13 mmol/L, sodium was 105.3 mmol/L, and chlorine was 70.9 mmol/L at the time of admission. The electrocardiogram showed sinus tachycardia, with a heart rate of 101 beats per minute. No anomalies were found in the head CT or the saddle region of MRI. After being admitted, the patient received nutritional support, potassium, and sodium supplements. The blood potassium level progressively returned to normal, but the blood sodium and chlorine level did not, occasionally reaching critical levels. During this hospital stay, the patient received clozapine, paliperidone, and sodium valproate sustained-release pills. The patient′s condition remained unaltered, and he continued to struggle with his inability to resist the urge to drink water. We tried to use fluoxetine hydrochloride tablets daily starting at 20 mg and progressively increasing to 60 mg. One month later, the patient′s water intake progressively dropped. Two months later, the blood′s levels of sodium and chlorine were back to normal.The patient was followed on seven months after being discharged, he was taking his medication as prescribed, and his condition was stable. His water intake also turned normal.

In clinical practice, the likelihood of low sodium and water poisoning should be considered when a mental patient exhibits sudden mental symptoms deterioration, convulsions, disturbance of consciousness, and other symptoms. Prompt rescue should be carried out to reduce mortality.