Inflammatory Thoracic Aortic Aneurysm in a Patient with Advanced Lung Adenocarcinoma Treated with Pembrolizumab

A 57-year-old man with lung adenocarcinoma was treated with chemotherapy and immune checkpoint blockade. After two cycles of carboplatin, pemetrexed, and pembrolizumab, he developed a persistent fever. Chest computed tomography (CT) suggested inflammation of the aortic wall. We treated the patient with corticosteroids. After four cycles of carboplatin, pemetrexed, and pembrolizumab, chest CT showed an aneurysm in the ascending aorta. We diagnosed him with inflammatory thoracic aortic aneurysm induced by pembrolizumab and performed surgical replacement of the ascending aorta. Although this might be a very rare case, we should be aware of aortitis as a potential adverse effect of pembrolizumab.