A case of suspected hydroxychloroquine-induced cardiomyopathy: From therapy to toxicity.

Background: Hydroxychloroquine (HCQ) is a cornerstone treatment for rheumatologic diseases. While it is generally well tolerated, chronic use has rarely been associated with cardiotoxicity. It is believed to occur due to the accumulation of HCQ in lysosomes, which impairs enzyme activity and eventually leads to myocardial fibrosis. Risk factors for HCQ-induced cardiotoxicity include older age, female sex, renal impairment, and prolonged or high cumulative exposure to HCQ. Case presentation: A 64-year-old female patient with systemic lupus erythematosus and mixed connective tissue disease presented with acute, severe decompensated heart failure that required intubation. She had been taking HCQ (200 mg daily) for 3 years. An echocardiogram 1-year prior showed HFrEF (EF 35% to 40%). Initial workup included a cardiac MRI, which revealed a severely dilated and hypertrophied left ventricle (LVEF 19%). An endomyocardial biopsy confirmed HCQ-induced toxicity, revealing characteristic myeloid bodies. Following discontinuation of HCQ, guideline-directed medical therapy for HFrEF was started. Over the following 9 months, she showed progressive recovery, with LVEF improving from 19% to 50% and NYHA functional class improving from III to II. Discussion: Hydroxychloroquine (HCQ)-induced cardiomyopathy is often under-recognized, especially in patients with moderate treatment durations, as its presentation can mimic other causes of heart failure. Early recognition is essential, as prompt discontinuation of HCQ may allow for meaningful recovery of cardiac function.