Hydroxychloroquine Cardiotoxicity and Sarcomeric Hypertrophic Cardiomyopathy

Hydroxychloroquine cardiotoxicity is a rare cause of dilated or restrictive cardiomyopathy.

A 50-year-old male with a prior clinical diagnosis of hypertrophic cardiomyopathy presented with monomorphic ventricular tachycardia. Cardiac magnetic resonance imaging (CMR) revealed biventricular hypertrophy and systolic dysfunction, with diffuse nonischemic fibrosis. Endomyocardial biopsy (EMB) revealed myocyte hypertrophy and interstitial fibrosis, consistent with hypertrophic cardiomyopathy, and vacuolated myocytes and myeloid bodies, consistent with hydroxychloroquine cardiotoxicity. Genetic testing found a heterozygous pathogenic MYBPC3 intronic variant, confirming the diagnosis of sarcomeric hypertrophic cardiomyopathy.

Hydroxychloroquine is an underrecognized cause of cardiotoxicity, particularly in patients with a preexisting cardiomyopathy. In the setting of preexisting cardiomyopathy with clinical deterioration and suspicion of a superimposed process, CMR, EMB, and genetic testing can provide diagnostic clarity and facilitate cascade screening.