Recurrent Nonbacterial Thrombotic Endocarditis after Vegetectomy of Bioprosthetic Mitral Valve

We report a case of recurrent nonbacterial thrombotic endocarditis (NBTE) following vegetectomy of bioprosthesis without malignancy or autoimmune disorders. A 76-year-old woman underwent mitral valve replacement with a bioprosthesis for mitral regurgitation. Six years later, an outpatient echocardiography revealed a mobile vegetation incidentally. No signs of infection were observed, and various tests ruled out malignancy or autoimmune disorders. Pathological findings after an urgent vegetectomy also showed no signs of infection, and the diagnosis was NBTE. Anticoagulation therapy with warfarin was continued, but 1 year after surgery, an outpatient echocardiography revealed NBTE recurrence. After the patient underwent anticoagulation therapy with heparin and resection of the papilloma of the maxillary sinus, the vegetation disappeared, and there has been no recurrence. Since NBTE can recur, strict lifelong follow-up with anticoagulation therapy might be required.