Nonbacterial Thrombotic Endocarditis Presenting with Leg Pain and a Left Atrial Mass Lesion.

Systemic lupus erythematosus (SLE) is a major cause of nonbacterial thrombotic endocarditis (NBTE) associated with intracardiac sterile vegetations. It is rare for vegetations to present as an atrial tumor. This report describes a 48-year-old female with SLE and antiphospholipid syndrome complicated by recurrent thrombosis on anticoagulation. A large left atrial mass lesion was detected on echocardiography during a work-up for leg burning. Infective endocarditis could not be confirmed, and hence left atrial mass lesion was the most likely diagnosis. The patient was managed surgically and the pathology report revealed fibrin networks in a pattern similar to that of thrombosis, characteristic of NBTE.