Acute Transient Psychotic Disorder — MRCPsych Paper B MCQ

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ModerateSchizophrenia & PsychosisAcute Transient Psychotic DisorderMRCPsych Paper B

A 23-year-old develops delusions and hallucinations over 5 days. The content and type of the psychotic symptoms change markedly from day to day. There is no sustained manic or depressive syndrome, no substance use or medical cause, and no previous psychotic illness. The symptoms fully remit within 3 weeks. According to ICD-11, what is the most likely diagnosis?

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Correct answer: C — Acute and transient psychotic disorder

The answer is C, acute and transient psychotic disorder. ICD-11 uses this diagnosis for an acutely developing, polymorphic psychosis in which symptoms change rapidly in type and intensity and the episode resolves completely within 3 months. The 5-day onset, markedly fluctuating delusions and hallucinations, and full remission after 3 weeks are the key discriminators. Schizophrenia requires a characteristic syndrome lasting at least 1 month and is not defined by this rapidly changing polymorphic presentation. Schizoaffective disorder requires both schizophrenia symptoms and a concurrent moderate or severe mood episode. Delusional disorder is predominantly a persistent delusional syndrome rather than a brief polymorphic psychosis with prominent hallucinations. Schizotypal disorder is an enduring pattern of eccentric behaviour and cognitive-perceptual abnormalities, not a fully remitting acute psychotic episode.

Reference: Falkai P et al. Psychotic disorders in ICD-11: the revisions, section on Acute and Transient Psychotic Disorder (6A23), 2020. https://pubmed.ncbi.nlm.nih.gov/33287579/