A 29-year-old man started on clozapine 3 weeks ago develops low-grade fever, sinus tachycardia of 120 per minute, and rising troponin I with a normal creatine kinase-MB fraction. Chest examination reveals a friction rub. What is the most likely diagnosis?
- A Neuroleptic malignant syndrome
- B Clozapine-induced eosinophilia
- C Clozapine-induced myocarditis ✓
- D Clozapine-induced cardiomyopathy
Correct answer: C. Clozapine-induced myocarditis
Explanation
Clozapine myocarditis occurs characteristically in the first 4 to 6 weeks of treatment, presenting with fever, tachycardia, chest discomfort, elevated troponin, and sometimes a friction rub. Cardiomyopathy is a later complication appearing after months to years. NMS features marked rigidity and grossly elevated creatine kinase, absent here. Eosinophilia peaks later and is usually asymptomatic. Any fever with tachycardia in the first month of clozapine demands urgent cardiac evaluation.
Reference: Maudsley Prescribing Guidelines in Psychiatry, 14th ed.
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