Cardiac Sarcoma Mimicking Libman–Sacks Endocarditis in a Patient with Systemic Lupus Erythematosus (SLE): A Case Report and Literature Review

We present the case of a 39-year-old woman who was diagnosed with SLE and antiphospholipid antibodies 8 years ago. The chief manifestations of her disease included low-grade fever and polyarthritis. Eight months before presentation, she experienced symptoms attributed to a flare of SLE, leading to an increase in immunomodulatory treatment with no improvement. She presented to the emergency room with acute onset of dyspnea. Clubbing of her fingers and toes was noted. When questioned, she reported the onset of clubbing 5 months earlier. A CTA was performed to rule out pulmonary embolism, which was excluded, although it revealed a severely damaged mitral valve with severe insufficiency and a large mass on the valve, protruding into the left atrium. Antibiotics were started, with a working diagnosis of infectious endocarditis; however, the severe mitral valve dysfunction lead to emergency mitral valve replacement, revealing an organized thrombus. She was treated with anticoagulation, with a working diagnosis of Libman–Sacks endocarditis, with no improvement. Additional immunosuppression failed to improve her symptoms. Enlargement of the thrombotic mass and an increased gradient across the prosthetic mitral valve led to repeat surgery, culminating in a diagnosis of high-grade sarcoma within the left atrial mass. We further discuss cardiac sarcoma and describe the occurrence of clubbing in patients with sarcoma. This case highlights the importance of interdisciplinary collaboration and the need for vigilant monitoring in refractory cases, particularly when atypical presentations arise.