Nonbacterial thrombotic endocarditis in antiphospholipid syndrome, presenting with severe mitral stenosis, heart failure, and stroke: case report.

Background: Nonbacterial thrombotic endocarditis (NBTE) is a rare cardiac manifestation of antiphospholipid syndrome (APS) and may also occur in patients with malignancy. It can mimic infective endocarditis or rheumatic mitral valve disease and often results in valvular disease and embolic complications. Case summary: A 39-year-old man with a 10-year history of primary APS presented with acute decompensated heart failure and left-sided weakness. Clinical examination revealed signs of biventricular failure, mid-diastolic and systolic murmurs, and neurological deficits. Transthoracic echocardiography (TTE) revealed severe mitral stenosis, large mitral valve masses, severe tricuspid regurgitation, and pulmonary hypertension. Brain magnetic resonance imaging (MRI) showed a lacunar infarct. Three sets of blood cultures were negative. Transoesophageal echocardiography (TEE) revealed large mobile masses on the mitral valve leaflets. The differential diagnosis included infective endocarditis and NBTE. In the setting of APS and the absence of fever, along with persistently negative blood cultures, NBTE was strongly suspected. Given the presence of severe obstructive mitral stenosis and a life expectancy exceeding one year, the management plan included valvular intervention in collaboration with a multidisciplinary team, alongside supportive therapy and anticoagulation. However, the patient declined surgical intervention and was therefore managed conservatively with optimized medical therapy and anticoagulation. On follow-up, the patient demonstrated clinical improvement with corresponding improvement in echocardiographic parameters. Discussion: NBTE should be considered in APS patients presenting with cardiac murmurs and embolic events. TTE is essential for diagnosis. This case underscores the importance of prompt identification and a multidisciplinary approach.