The Heart of the Thymus: A Rare Tale of Nonischemic Cardiomyopathy in the Absence of Myasthenia Gravis.

Thymomas are rare epithelial tumors of the anterior mediastinum known for their association with autoimmune and paraneoplastic syndromes, most notably myasthenia gravis (MG). Cardiomyopathy is an exceptionally rare paraneoplastic manifestation. Emerging case reports suggest that thymoma may exert systemic effects independent of MG, including direct or immune-mediated myocardial injury. We report the case of a 54-year-old male with known nonischemic cardiomyopathy who presented with septic shock from pneumonia and cholecystitis, complicated by ventricular arrhythmias and decompensated heart failure. Imaging revealed a calcified anterior mediastinal mass, later diagnosed as a World Health Organization (WHO) type B thymoma. Notably, the patient lacked any clinical or serologic evidence of MG or other autoimmune syndromes. Cardiac magnetic resonance imaging (MRI) excluded myocarditis and takotsubo cardiomyopathy, while coronary angiography ruled out ischemic disease. Despite anticoagulation, a persistent left ventricular (LV) thrombus remained. The patient's cardiac dysfunction necessitated mechanical ventilation, vasopressors, and a multidisciplinary heart failure regimen. This case expands the phenotype of thymoma beyond the traditional paraneoplastic spectrum. It reinforces the need for heightened clinical suspicion and a multisystem diagnostic approach in cases of unexplained cardiomyopathy. Further investigation into immune-mediated cardiac injury in thymoma is warranted.