Long-term hydroxychloroquine use resulting in cardiomyopathy and conduction abnormalities: a case report.

Background: Diagnosing the cause of undifferentiated left ventricular hypertrophy (LVH) in a patient with progressive heart failure symptoms can present a diagnostic challenge, with potential for both inherited and acquired aetiologies. Hydroxychloroquine-induced cardiomyopathy (HCQ-CM) is a rare complication of long-term hydroxychloroquine use. This case report highlights its clinical presentation, key differential diagnoses, and treatment strategies. Case summary: A 56-year-old female with a longstanding history of systemic lupus erythematosus presented with progressive dyspnoea, fatigue, and fluid overload. Initial investigation revealed LVH with restrictive physiology, elevated cardiac biomarkers, and non-specific findings on echocardiography suggestive of an infiltrative cardiomyopathy. The diagnosis remained uncertain until an endomyocardial biopsy (EMB) confirmed HCQ-CM, characterized by the presence of curvilinear inclusion bodies. Following cessation of HCQ, there was a significant clinical improvement, with the patient achieving NYHA class I status at 6 months follow-up. Conclusion: This case highlights the critical importance of considering HCQ-CM, in the differential diagnosis of unexplained heart failure and LVH in patients on long-term HCQ therapy. A multi-parametric diagnostic approach-including EMB and genetic testing where appropriate-is essential to identify potentially reversible causes of cardiomyopathy and enable timely therapeutic adjustments.