Infectious aortic aneurysm caused by Streptococcus pneumoniae serotype 10: A case report

Streptococcus pneumoniae is a leading pathogen responsible for both respiratory and invasive infections. Infectious aortic aneurysm (IAA) caused by S. pneumoniae is rare, and few cases have reported the associated serotype. We describe a case of IAA due to S. pneumoniae serotype 10 in an unvaccinated 50-year-old man with no prior medical history. The patient presented with progressive anterior chest pain, and contrast-enhanced computed tomography revealed a saccular aneurysm of the descending aorta. Emergency thoracic endovascular aneurysm repair (TEVAR) was performed. Blood cultures yielded S. pneumoniae, later identified as serotype 10. Although the strain was susceptible to penicillin G and blood cultures collected on day 6 were negative after initiation of antibiotic treatment, the aneurysm did not respond to antimicrobial therapy and continued to enlarge, requiring open surgical graft explantation. The patient was ultimately discharged uneventfully, with no recurrence. To the best of our knowledge, this is the first documented case of IAA caused by S. pneumoniae serotype 10. In this case, early diagnosis and a multidisciplinary approach, including staged surgical interventions, were critical to the successful outcome. Despite no evident immunodeficiencies, the patient was unvaccinated, reflecting Japan's current policy for adults under 65. The involvement of a non-vaccine serotype highlights the potential value of re-examining vaccination strategies and gaining more insight into rare manifestations like pneumococcal IAA.