We present a case report of a 65-year-old gentleman who presented with an aortoenteric fistula along with a review of the literature. He was found, in addition, to have an inflammatory infrarenal aortic aneurysm with a posterior rupture. Cultures of the aneurysm sac confirmed a Streptococcus pneumoniae infection. The patient had previously presented with pneumonia. Antibody testing revealed an isolated pneumococcal IgG deficiency. The case demonstrates the diverse pathologies associated with aortic aneurysms and a need to be vigilant and occasionally expect the unusual.