Anti-NMDA receptor encephalitis — MRCPsych Paper A MCQ

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ModerateNeuroimaging, neuroendocrinology and psychoneuroimmunologyAnti-NMDA receptor encephalitisMRCPsych Paper A

A 20-year-old woman develops a viral-like prodrome followed over 10 days by agitation, paranoid delusions and auditory hallucinations. She subsequently has generalised seizures, prominent orofacial dyskinesia and fluctuating blood pressure and heart rate. There has been no exposure to recreational drugs, serotonergic medication or dopamine-receptor antagonists. What is the most likely diagnosis?

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Correct answer: C — Anti-NMDA receptor encephalitis

The correct answer is **anti-NMDA receptor encephalitis**. Its characteristic evolution in a young woman includes a viral-like prodrome, acute psychiatric disturbance, seizures, movement disorder—particularly orofacial dyskinesia—and autonomic instability. Herpes simplex encephalitis remains an important urgent differential but more often produces fever, impaired consciousness and focal neurological features; it does not as characteristically produce this neuropsychiatric–dyskinetic sequence. Serotonin syndrome requires serotonergic exposure and usually causes clonus, hyperreflexia and gastrointestinal symptoms. Neuroleptic malignant syndrome requires dopamine-antagonist exposure and is associated with severe rigidity and hyperthermia. First-episode schizophrenia cannot adequately explain seizures, dyskinesia and autonomic instability.

Reference: Barry H, Byrne S, Barrett E, et al. Anti-N-methyl-D-aspartate receptor encephalitis: review of clinical presentation, diagnosis and treatment. BJPsych Bulletin. 2015;39(1):19–23. https://pubmed.ncbi.nlm.nih.gov/26191419/