Which syndrome is described by polydipsia, intermittent hyponatremia, and psychosis?

• A. PIP syndrome
• B. SIADH
• C. Neuroleptic malignant syndrome
• D. Akathisia

Answer: (A)

This scenario highlights a pattern where excessive water intake in a person with psychosis leads to low sodium levels that can fluctuate. Polydipsia means the person drinks a lot of water. When water intake is high enough, the kidneys can’t dilute the urine quickly enough, so serum sodium drops—hyponatremia. In someone with psychosis, polydipsia is a recognized behavior, so the combination of polydipsia, intermittent hyponatremia, and psychosis describes this specific syndrome.

This is different from SIADH, where hyponatremia comes from inappropriate antidiuretic hormone activity with concentrated urine and not typically tied to polydipsia. Neuroleptic malignant syndrome and akathisia are not about water balance or hyponatremia; they present with hyperthermia/rigidity or restlessness, respectively, rather than a triad of polydipsia and hyponatremia tied to psychosis.

So the pattern of excessive water intake causing intermittent hyponatremia in a psychotic patient points to this PIP syndrome. Management focuses on addressing the polydipsia, implementing fluid restriction, and carefully correcting sodium while monitoring for neurologic symptoms.