Neuroleptic malignant syndrome — MRCPsych Paper A MCQ

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ModeratePsychopharmacologyNeuroleptic malignant syndromeMRCPsych Paper A

A 26-year-old man with schizophrenia has his haloperidol dose increased. Two days later, he becomes confused and diaphoretic, with a temperature of 39.4°C, tachycardia and labile blood pressure. Examination shows severe generalised rigidity, normal tendon reflexes and no clonus. His serum creatine kinase is 4,200 IU/L. Which adverse drug reaction is the most likely diagnosis?

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Correct answer: D — Neuroleptic malignant syndrome

This is neuroleptic malignant syndrome: a recent haloperidol dose increase is followed by hyperthermia, altered mental state, autonomic instability, severe generalised rigidity and markedly elevated creatine kinase. Antipsychotic treatment should be stopped immediately, with urgent medical assessment, monitoring and supportive management. Serotonin syndrome can also cause fever and confusion but typically features neuromuscular excitation, especially clonus and hyperreflexia, which are absent here. Acute dystonia causes focal or generalised sustained contractions, such as torticollis or an oculogyric crisis, without this systemic syndrome. Anticholinergic toxicity more often causes dry skin, mydriasis, urinary retention and reduced bowel sounds. Malignant hyperthermia is usually triggered by susceptible anaesthetic agents or suxamethonium.

Reference: electronic Medicines Compendium. Haloperidol 5 mg/ml solution for injection, Summary of Product Characteristics, section 4.4: Neuroleptic malignant syndrome. Current SmPC accessed 15 August 2026. https://www.medicines.org.uk/emc/product/101458/smpc