Rapid Resolution of Apophenic Psychosis With Low-Dose Olanzapine in Very Late-Onset Schizophrenia-Like Psychosis.

Very late‑onset schizophrenia‑like psychosis (VLOSLP) presents diagnostic complexity due to the broad range of medical, neurological, and psychiatric conditions that can manifest with late‑life psychosis. We describe a case of a man in his mid‑70s who developed progressive apophenic experiences, characterised by the perception of patterns, rhythms, and "algorithms" in everyday environments, leading to referential beliefs and behavioural change. Investigations showed normal blood tests, preserved cognitive screening scores, and MRI evidence of chronic white matter ischaemic changes and diffuse cerebral atrophy. Differential diagnoses included vascular psychosis, autoimmune encephalitis, obsessive-compulsive disorder with poor insight, and neurodegenerative disease; however, the overall presentation was most consistent with VLOSLP. The patient was treated using a bio‑psycho‑social approach, with limited response to quetiapine but rapid and sustained remission following initiation of low‑dose olanzapine. Symptom recurrence after dose reduction further supported a primary psychotic process. This case highlights an atypical presentation of VLOSLP dominated by apophenia and underscores the importance of thorough assessment and cautious, individualised antipsychotic treatment in older adults.