Right atrial thrombus mimicking myxoma in antiphospholipid syndrome with secondary immune thrombocytopenic purpura

[Abstract] A 22-year-old woman was referred to our hospital due to a large right atrial mass. Echocardiography showed the mass to be pedunculated, mobile, partially calcified, internally heterogeneous, and with a rough surface. Computed tomography showed internal calcification and heterogeneity. On magnetic resonance imaging, the mass was isointense to hypointense on T1-weighted images and hypointense to hyperintense on T2-enhanced images. Simultaneously, laboratory work-up revealed antiphospholipid syndrome (APS) with secondary immune thrombocytopenic purpura (ITP). We could not definitively differentiate between myxoma or cardiac thrombus associated with APS. Preoperatively, the patient was administered γ-globulin and methylprednisolone due to ITP. Surgical resection of the mass was performed in order to avoid incarceration to the tricuspid valve or embolization. Based on gross and histologic findings, the cardiac mass was diagnosed as a thrombus. She was discharged with no postoperative bleeding. APS-associated cardiac thrombus is rare. It is difficult to distinguish APS-associated cardiac thrombus from myxoma. Moreover, ITP sometimes occurs as a complication in patients with APS. We experienced a case of right atrial thrombus mimicking myxoma in a patient with APS and secondary ITP.