Clozapine Monitoring — MRCPsych Paper B MCQ

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ModerateSchizophrenia & PsychosisClozapine MonitoringMRCPsych Paper B

A 34-year-old woman develops a temperature of 38.5°C and persistent resting tachycardia during the third week after starting clozapine. Her C-reactive protein and troponin are elevated, and an ECG shows sinus tachycardia. She has no cough, hypoxia, pleuritic chest pain, muscle rigidity or altered consciousness. What is the most likely diagnosis?

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Correct answer: B — Clozapine-induced myocarditis

The most likely diagnosis is **clozapine-induced myocarditis**. It occurs predominantly during the first two months of clozapine treatment. Fever and persistent resting tachycardia are important warning features, while raised troponin indicates myocardial injury and elevated CRP supports an inflammatory process. A normal or non-specific ECG showing only sinus tachycardia does not exclude myocarditis. Benign clozapine-related fever can occur during the first three weeks, so timing alone does not distinguish it; the troponin elevation makes it inappropriate here. Pneumonia and pulmonary embolism are less likely without respiratory symptoms or hypoxia. Neuroleptic malignant syndrome would usually involve prominent rigidity, altered mental state and other evidence of systemic muscle injury rather than isolated myocardial-marker elevation.

Reference: Viatris Products Limited. Clozapine Viatris 200 mg Tablets: Summary of Product Characteristics, sections 4.4 (Cardiovascular disorders and Fever), revised February 2026. https://www.medicines.org.uk/emc/product/102058/smpc