Ruptured mycotic pseudoaneurysm of the thoracic aorta.

A 68-year-old man being treated for a Staphylococcus aureus bacteremia developed hemoptysis. A transesophageal echocardiogram (TEE) and computed tomographic (CT) scan showed a large descending thoracic aorta pseudoaneurysm. The patient died before surgical intervention could be performed. Pathological examination revealed the presence of a saccular pseudoaneurysm originating from a mural defect at the site of an ulcerated atherosclerotic plaque. There was rupture into the mediastinum with contained hematoma. Microscopic examination documented numerous Gram-positive bacterial cocci at the rupture site.