Septal atrial thrombosis as a primary presentation of antiphospholipid syndrome in a patient with ANA-negative systemic lupus erythematosus: a case report.

Introduction and importance: Systemic lupus erythematosus (SLE) predominantly affects young women and is associated with an increased risk of thrombosis. Antiphospholipid antibody syndrome (APS) may complicate the clinical picture, often leading to recurrent arteriovenous thrombosis. This case report underscores the significance of two unique aspects: the rare occurrence of an atrial thrombus and the presence of antinuclear antibody (ANA)-negative SLE. Case presentation: A 32-year-old woman presented with a history of symmetric polyarticular joint pain, oral ulcers, significant weight loss, and a history of unprovoked popliteal thrombosis and two unexplained abortions. One week prior to admission, she experienced severe headaches and elevated blood pressure. Clinical evaluation revealed several abnormalities, including a systolic murmur, livedo reticularis, and a transthoracic echocardiogram showing severe mitral regurgitation and an atrial thrombus. A transesophageal echocardiogram confirmed the presence of a pedunculated lesion in the right atria, challenging differential diagnosis. Clinical discussion: ANA-negative SLE, though rare, was observed in this patient, highlighting diagnostic complexities. APS compounded the clinical presentation, emphasizing the importance of identifying specific autoantibodies and recurrent thrombotic events. In the case of atrial thrombus, differentiation from other cardiac conditions, such as myxoma or vegetation, is a key. Conclusions: This case underscores the critical importance of recognizing and managing atrial thrombus, a rare but life-threatening complication in patients with systemic lupus erythematosus and antiphospholipid syndrome. Additionally, the diagnostic challenge of ANA-negative SLE warrants careful consideration in patients presenting with characteristic features of the disease.