Hydroxychloroquine-induced cardiomyopathy: a novel case highlighting the role of electron microscopy in diagnosis

Hydroxychloroquine-induced cardiomyopathy is a rare adverse reaction with serious and potentially fatal outcomes. We report a 56-year-old female who presented in acute right heart failure with NYHA class III symptoms, ascites, raised JVP pressure, and peripheral oedema. Significant medical history included SLE (diagnosed in her late 20s, well controlled on hydroxychloroquine), CKD, and poorly controlled hypertension. Extensive investigations included transthoracic ECHO, cardiac MRI, cardiac amyloidosis scan, and right heart catheter. Left ventricular hypertrophy, pulmonary hypertension, severe restrictive cardiomyopathy, and heart failure with preserved ejection fraction (LVEF 66%) were determined. There were no features of infiltrative cardiomyopathy, including cardiac amyloidosis, and Fabry screening was negative. Due to uncertain aetiology the patient underwent cardiac biopsy. Light microscopy revealed myocyte disarray and glycogen vacuolation with no inflammation. Amyloid was not identified. Electron microscopy revealed extensive myeloid figures and occasional curvilinear bodies within the cardiac myocytes, confirming hydroxychloroquine-induced cardiomyopathy. After cessation of the drug, the patient made a significant recovery with reduction to NYHA class I symptoms. This case adds to the body of literature regarding this rare adverse drug reaction and highlights the importance of electron microscopy in cardiomyopathy diagnosis.