[Inherited metabolic disease presenting as a psychiatric disorder].

A 25-year-old man with autism was admitted for suspected psychosis. He had jaundice, abnormal liver tests, splenomegaly, and progressive cognitive decline with vertical gaze palsy. Antipsychotics and ECT were ineffective. Family history (sister with cognitive problems and splenomegaly) prompted genetic testing, revealing two pathogenic NPC1 variants, confirming Niemann-Pick type C. This case highlights a rare adult-onset psychiatric NPC and the importance of early multidisciplinary assessment and relative involvement.