An 18-year-old female suffered from chest oppression on effort for a month. She visited a hospital, and her electrocardiogram showed ST-segment depression in leads I, aVL, and V2–4. She was suspected of having angina pectoris, and was referred to our hospital. Her laboratory data on admission showed a normal range of creatinine kinase and troponin I as shown in Table. Echocardiography revealed normal left ventricular contraction and mild to moderate aortic regurgitation. Coronary angiography showed severe stenosis in the ostium of both the left main trunk and the right coronary artery. Quantitative coronary angiography analysis was performed with a computerized quantitative analysis system (QAngio XA version 7.3, Medis Medical Imaging System, Leiden, The Netherlands), using a contrast-filled catheter as a calibration source. The percentage of the diameter of the most severe stenosis compared with the reference diameter was defined as % diameter stenosis []. % diameter stenosis of the ostial stenosis was 95.0% in the left main trunk and 87.2% in the right coronary artery. Intra-coronary administration of isosorbide dinitrate did not dilate the coronary ostial stenosis, suggesting that the stenosis was an organic lesion. Optimal medical treatment, including beta-blocker, antiplatelet, and statin, was initiated for her coronary artery disease. Contrast-enhanced CT showed no specific abnormality of the aorta. She did not have renal artery stenosis or hypertension. Her right and left ankle-brachial indices were 1.08, and 1.03, respectively. She was examined by an ophthalmologist and did not have vision impairment. Magnetic resonance angiography revealed no significant stenosis of her carotid artery. The patient had no coronary risk factors or signs of infectious disease and congenital heart disease. C-reactive protein, serum amyloid A, and erythrocyte sedimentation rate (1 h) on admission were 2.13 mg/dL (normal range: 0.00–0.30 mg/dL), 479 μg/mL (normal range: 0.0–8.0 μg/mL), and 40 mm (normal range: 3–15 mm), respectively, suggesting systemic inflammation. 18F-FDG PET/CT showed isolated inflammation of the aortic root. She was therefore diagnosed with Takayasu arteritis, and oral administration of prednisolone was started from 0.56 mg/kg/day. Tocilizumab was added 3 months after the initiation of prednisolone. Follow-up coronary angiography showed regression of the ostial stenosis 4 months after the initiation of prednisolone, and % diameter stenosis was 86.7% in the left main trunk and 72.6% in the right coronary artery. Intravascular ultrasound or optical coherence tomography was not performed for the ostial lesions. Her C-reactive protein and erythrocyte sedimentation rate (1 h) were decreased to 0.03 mg/dL and 5 mm, respectively. The second 18F-FDG PET/CT showed decreased 18F-FDG uptake in the aortic root, but still showed inflammation. Her serum amyloid A of 13.8 μg/mL was not normalized, therefore we decided to control the disease activity by combined immunosuppressive treatment including steroid pulse therapy (methylprednisolone 1 g/day for 3 days). Oral methotrexate ranging from 4 to 8 mg/week was administered to decrease corticosteroid dose. The levels of serum amyloid A were not significantly increased and the dose of prednisolone was decreased from 0.28 to 0.21 mg/kg/day after administration of methotrexate. Myocardial perfusion imaging with 13N-ammonia PET detected myocardial ischemia. Coronary artery bypass surgery was considered after the suppression of disease activity, but the patient and her family rejected invasive revascularization for coronary artery disease. After immunosuppressive treatment with prednisolone, tocilizumab and methotrexate, chest oppression and ST-segment depression was not observed. She was discharged after a 201-day hospitalization and administered 0.21 mg/kg/day of prednisolone, 8 mg/week of methotrexate, 162 mg/week of tocilizumab, 40 mg/day of isosorbide dinitrate, 15 mg/day of nicorandil, 100 mg/day of aspirin, 2.5 mg/day of rosuvastatin, and 10 mg/day of carvedilol. Electrocardiogram at rest revealed no significant ST-T change, and laboratory data showed no significant increase of C-reactive protein, erythrocyte sedimentation rate (1 h), or serum amyloid A in the ambulatory follow-up. She had no cardiac events for 6 months after discharge.