[Right Atrium Thrombus Due to Cardiac Amyloidosis;Report of a Case].

: A 51-year-old man complaining of exertional dyspnea and syncope was admitted to our hospital. Computed tomography(CT) and transesophageal echocardiography demonstrated a mobile tumor-like lesion in the right atrium. Surgical resection was performed under cardioplegic arrest, which revealed an organized thrombus. Pathological examination revealed amyloid deposition in the myocardium, and bone marrow biopsy revealed CD138 (+) stem cells. Therefore, the patient was diagnosed with amyloid light-chain (AL) amyloidosis associated with multiple myeloma. Although he required percutaneous cardiopulmonary support for postoperative right heart failure for 3 days, he recovered well and was discharged from the hospital on day 44, in a good condition. He was treated with bortezomib for multiple myeloma after surgery. Thus, despite the maintenance of sinus rhythm, intra-cardiac thrombus could be formed with amyloidosis.