Anti-phospholipid syndrome (APS) is defined by thrombosis (venous, arterial, or small vessel) and/or pregnancy morbidity (recurrent miscarriage, fetal loss, or placental insufficiency) occurring in the presence of persistently positive anti-phospholipid antibodies (aPL), lupus anticoagulant (LAC) test, anti-cardiolipin antibodies (aCL), and anti-B2-glycoprotein I antibodies [1]. Anti-phospholipid syndrome can occur as an isolated condition or can be associated with connective tissue diseases, most commonly systemic lupus erythematosus (SLE). Herein we present a patient with aPL syndrome and cardiac involvement, misdiagnosed and treated as infective endocarditis.A 31-year-old woman was admitted to the neurology clinic because of weakness of the left hand. Her clinical history revealed mild weakness of bilateral hands lasting less than 2 h for about 5 years. Cranial contrast magnetic resonance imaging (MRI) showed atrophic gliotic changes and thin strip style gyral hyperintensity in T1 imaging at the superior sylvian fissure. Also gliotic localized atrophic changes were observed at the right posterior horn of the lateral ventricle. The patient was referred to the cardiology department for differential diagnosis. Initial physical examination and electrocardiography were evaluated as normal. Transthoracic and then transesophageal echocardiography revealed a hypodense fibrillated mobile 5 mm mass at the A2 scallop of the anterior mitral valve leaflet and moderate mitral regurgitation (Figures 1-3). Both MRI and transesophageal echocardiography (TEE) findings were consistent with endocarditis, so the patient was admitted to the cardiology department and consulted with rheumatology and infectious diseases. An empiric antibiotic regimen was started after blood culture sampling. Meanwhile her laboratory findings demonstrated all increased positive results of anti-b-2-glycoprotein-1 IgM and IgG, lupus anticoagulant, anti-cardiolipin IgM and IgG and decreased C4 levels. She had no fever and blood cultures were negative, so antibiotherapy was stopped at day 10, with the final diagnosis of primary APS and Libman-Sacks endocarditis. She was discharged with warfarin therapy.The common cardiac manifestations of APS include valvular involvement such as thickening, vegetations and dysfunction, coronary thrombosis, ventricular hypertrophy and dysfunction, intracardiac thrombi and pulmonary hypertension [2]. The most common echocardiographically