Rapidly Progressive Infectious Pseudoaneurysm of the Ascending Aorta Caused by Streptococcus agalactiae: A Case Report and Literature Review.

INTRODUCTION: Infectious aortic aneurysms are uncommon but life-threatening conditions associated with high mortality. Although they account for less than 3% of all aortic aneurysms, their clinical course may be rapidly progressive. Streptococcus agalactiae is a rare cause of infectious aortic aneurysm. We report a case of a rapidly progressive infectious pseudoaneurysm of the ascending aorta caused by S. agalactiae in an elderly woman with untreated diabetes. CASE PRESENTATION: A 77-year-old woman with untreated diabetes presented with fever and malaise and was initially diagnosed with a left renal abscess at a referring hospital. Blood cultures grew S. agalactiae, and intravenous antibiotics were started. Despite treatment, contrast-enhanced CT performed 6 days after admission revealed a newly developed, rapidly enlarging 65-mm pseudoaneurysm of the ascending aorta. She was urgently transferred to our institution and underwent emergency ascending aortic replacement under hypothermic circulatory arrest. Intraoperative findings revealed a saccular pseudoaneurysm containing purulent material, consistent with an infectious process. Postoperatively, she received 6 weeks of intravenous antibiotics followed by oral suppressive therapy. Her postoperative course was uneventful, and no recurrence was observed during 2 years of follow-up. CONCLUSIONS: Infectious aortic aneurysms caused by S. agalactiae are extremely rare but may progress rapidly despite appropriate antibiotic therapy. Patients with risk factors such as advanced age and poorly controlled diabetes may have a particularly aggressive disease course. Early CT evaluation, close clinical monitoring, and timely surgical intervention are essential for preventing catastrophic complications.