A 14-year-old girl was admitted because of dyspnea. She was treated for ulcerative colitis 5 years earlier. A weak pulse was observed in both upper extremities with isolated high blood pressure in the left lower leg. The C-reactive protein level was 6.29 mg/dl and the erythrocyte sedimentation rate was 120 mm/h. Echocardiography showed a dilated left ventricle with a large mural thrombus (A,Online Video 1) and dilated ascending aorta (B). Three-dimensional computed tomography showed a dilated and tortuous ascending and descending aorta with multiple stenoses of the aortic branches (C), including 50% stenosis of the right proximal renal artery and total occlusion of the left renal artery (D). Coronary angiography showed no stenosis (E,Online Videos 2, 3, and 4). Having determined a diagnosis of Takayasu arteritis associated with ulcerative colitis and a dilated left ventricle with thrombus, we prescribed an oral prednisolone as a steroid, oral hydrochlorothiazide and spironolactone as a diuretic, enalapril, and subcutaneous enoxaparin followed by warfarin. After 6 weeks of treatment, the left ventricular thrombus was dissolved completely and left ventricular function improved slightly (F,Online Video 5). Asc. Ao = ascending aorta; LV = left ventricle.