A case of nonbacterial thrombotic endocarditis following immune checkpoint inhibitor treatment for lung adenocarcinoma

Abstract

Background: Nonbacterial thrombotic endocarditis (NBTE) is a rare condition characterized by the formation of sterile, fibrin vegetations on cardiac valve leaflets and can cause critical systemic embolization. The etiology of NBTE is associated with a hypercoagulable state. Case: A 66-year-old woman was diagnosed with primary lung adenocarcinoma (cT2aN3M0, Stage HIB). She received 4 cycles of chemotherapy with carboplatin and pemetrexed following 9 cycles of pemetrexed monotherapy. Her lung cancer progressed after 17 months of first-line chemotherapy, so immune checkpoint inhibitor treatment with atezolizumab was started as second-line therapy. Several weeks after the administration of atezolizumab, she suffered from generalized edema and dull throbbing pain in her left leg. She was diagnosed with deep vein thrombosis, and edoxaban was started. Monoparesis of the right arm developed, and she visited the emergency room due to passage of bloody stool. Enhanced computed tomography (CT) scan showed arterial embolism of the right brachial artery, renal infarction of the right kidney, and active bleeding in the ascending colon. Diffusion magnetic resonance imaging revealed acute multiple brain infarction. Transesophageal echocardiography revealed a vegetation on the mitral valve, and we diagnosed her with thrombotic endocarditis associated with a hypercoagulable state due to advanced malignancy. Mitral valve replacement was performed, and the microscopic findings of the vegetation suggested NBTE. She received docetaxel alone and prompt initiation of continuous heparin infusion and was discharged 8 weeks after the operation. Conclusion: We should therefore consider the risk of NBTE after administering immune checkpoint inhibitors to treat lung cancer in patients developing systemic thromboembolism.