Mitral Valve Nonbacterial Thrombotic Endocarditis Associated With Antiphospholipid Syndrome in a Male Patient: A Comprehensive Case Report

Nonbacterial thrombotic endocarditis (NBTE) is a rare cardiac disease with a nonspecific presentation associated with hypercoagulable states including malignancy and autoimmune disorders, such as antiphospholipid syndrome (APS) and systematic lupus erythematosus. A 34-year-old male with a history of pulmonary thromboembolism presented to the hospital complaining of chest pain as an initial symptom. Transthoracic echocardiography revealed the presence of a mass-like lesion adhering to the anterior leaflet of the mitral valve. Once infective endocarditis was excluded, further imaging studies suggested that the cardiac neoplasm was the primary cause of the patient's symptoms, and the patient underwent surgical excision of mass along with mitral valve replacement. Microscopic analysis of the removed mitral valve mass indicated the presence of fibrotic tissue with thick collagen bundles and no inflammatory infiltrates, supporting the diagnosis of NBTE. Investigations for underlying conditions demonstrated persistent elevated titers of anti-β2 glycoprotein I IgG, supporting a diagnosis of APS. The patient was started on warfarin therapy with a closely monitored International Normalized Ratio (INR). After 6 months of follow-up, the patient reported no complications. This case highlights the importance of considering NBTE as a potential differential diagnosis in patients with intracardiac mass and inspecting associated conditions such as APS, as well as challenges encountered in diagnosis and management.