We describe the first case report of a mycotic abdominal aortic aneurysm secondary to Capnocytophaga canimorsus in an immunocompetent 65-year-old man. The exposure occurred after his dog scratched his arm and subsequently licked the wound. A review of C. canimorsus, a rarely pathogenic but potentially devastating bacterium, is also presented. CASE REPORTA 65-year-old male presented to his local emergency department with 3 days of lower abdominal pain, nausea, vomiting, fevers, and chills. Additionally, the patient had new midline low back pain, progressive over the preceding 3 months that acutely worsened over the 3 days prior to admission. A noncontrast computed tomography (CT) scan of the abdomen revealed a 5.8-cm para-renal abdominal aortic aneurysm (AAA) extending to just above the aortic bifurcation (Fig. 1). The aneurysm contacted the anterior aspect of the first and second lumbar vertebral bodies, and its indistinct margins were suggestive of a leak. The AAA was not a typical fusiform degenerative type, but a localized phenomenon of concern for either a penetrating atheromatous ulcer or a mycotic aneurysm. The patient was emergently transferred to our institution for surgical intervention.His past medical history included hypertension, hyperlipidemia, coronary artery disease, and prostate carcinoma with radical prostatectomy in 2001. The patient had no known history of an abdominal aortic aneurysm and had undergone CT scanning 3 years prior during evaluation of his prostate cancer. The patient was a United States Postal Service mail carrier who lived with his wife and two dogs. He smoked one to two packs of cigarettes daily, and although he had previously used alcohol heavily, he had not consumed any for over 15 years.Upon arrival at our institution, the patient's temperature was 100.9°F (38.2°C), the heart rate was 105/min, the respiratory rate was 20/min, and the blood pressure was 138/78 mm Hg. Physical examination revealed a soft abdomen with a faint, macular, purpuric rash, but no palpable aorta. He was tachycardic without a cardiac murmur. His lower extremities were cool, with palpable pulses throughout. Laboratory evaluation revealed a white blood cell count of 21,000/cubic mm, hemoglobin of 16.8 g/dl, blood urea nitrogen of 31 mg/dl, and creatinine of 2.0 mg/dl. The patient was emergently taken to the operating room for repair of a presumed ruptured AAA.During surgery, the aortic wall was thick with surrounding inflammatory debris and pus, but was without acute hemorrhage. A large posterior aortic perforation opened directly onto the spine, appearing to be a penetrating ulcer that had eroded through the aortic wall; however, given the patient's low-grade fever, leukocytosis, and operative findings of aortic wall inflammation and pus, an infectious etiology was considered. A sample of aortic wall and peri-aortic debris was sent for gram stain, culture, and histopathology (Fig. 2). The aorta was successfully repaired with a Dacron graft.The gram stain from the aortic wall revealed neutrophils but no...