Abstract

Early-onset neurocognitive disorders may initially present predominantly with psychiatric symptoms and can therefore be mistaken for primary psychotic disorders. A 42-year-old man with no previous psychiatric illness or history of substance use presented with an abrupt onset of recurrent formed visual hallucinations, consisting of seeing a snake emerging from a hole in the wall and subsequently moving along the walls of his house. He developed persecutory beliefs that someone had deliberately placed the snake to harm him, accompanied by hypervigilance, severe sleep disturbance, irritability, aggression toward family members, social withdrawal, and reduced appetite. Three days before admission, he wandered away from home and was subsequently found in a dishevelled and perplexed state, unable to recall where he had been. Schizophrenia was initially considered. However, mental status examination demonstrated impaired attention, recent and remote memory, abstract thinking, insight, and judgement. His Mini-Mental State Examination score was 12/30. Routine investigations, including hepatic, renal, thyroid and vitamin B12 assessments, were within normal limits. Magnetic resonance imaging of the brain demonstrated bilateral periventricular and deep white-matter hyperintensities consistent with chronic ischemic changes, together with cerebral volume loss and frontal-predominant atrophy. Following neurological assessment, the diagnosis was revised to earlyonset major neurocognitive disorder with psychotic symptoms, with a possible vascular contribution. The case illustrates how early-onset neurocognitive disorders may present to psychiatric services with prominent symptoms of psychosis. Marked cognitive impairment, disorientation, and structural abnormalities on neuroimaging should prompt consideration of an underlying neurological disorder rather than assuming a primary schizophrenia-spectrum illness.

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