Infected Thoracic Aortic Aneurysm Caused by Helicobacter cinaedi.

The causative organism is not identified in some cases of infected aneurysms, a life-threatening condition. A 68-year-old man presented with chest/back pain and a 1-year history of intermittent fever and fatigue. Computed tomography revealed a thoracic aortic aneurysm. After several negative blood cultures, he was eventually diagnosed with an infected aneurysm caused by Helicobacter cinaedi via gene analysis of an aortic tissue specimen. As H. cinaedi is a low-virulence bacterium, infection with this pathogen should be suspected in cases of aortic aneurysms with unidentified causative organism and a long history of subjective symptoms. Detailed examinations, including polymerase chain reaction, should be conducted in such cases.