[Periaortic gas and signs of dissection of a mycotic aneurysm in the descending thoracic aorta due to Clostridium septicum].

The case of 92-year-old male with a history of sepsis due to Clostridium septicum is described. Since the bacteria were also found at the site of joint aspiration, the patient underwent knee prosthesis removal. Due to the association between colorectal cancer and Clostridium septicum, a colonoscopy was performed. An adenocarcinoma was extracted in situ. At 5 months, the patient presented again with shortness of breath, acute retrosternal pain and fever. CT revealed a mycotic aneurysm of the descending aorta with Stanford B dissection and periaortic gas. Due to the fragility of the patient, conservative treatment was initiated.