Ruptured mycotic common iliac aneurysm due to Capnocytophaga canimorsus, acquired from dog saliva: A case report

INTRODUCTION: Mycotic arterial aneurysm occurs secondary to infection of the arterial wall Dubois et al. (2010). It is a serious clinical condition associated with significant morbidity and mortality. Various pathogens can be responsible but the most commonly isolated causative organisms are Staphylococcus spp. and Salmonella spp. Brown et al. (1984). An extremely uncommon causative pathogen is Capnocytophaga canimorsus, a commensal bacterium found in the normal gingival flora of canines. PRESENTATION OF CASE: We describe the case of a ruptured mycotic common iliac aneurysm presenting with acute haemodynamic instability and femoral nerve impairment due to compression secondary to extensive haematoma. Rupture was preceded by a four-week history of left hip/groin discomfort with an abrasion to the left upper limb exposed to dog saliva in the weeks prior to symptom onset. Open debridement, revascularisation, and aggressive antimicrobial therapy was utilised with microbiological culture revealing Capnocytophaga canimorsus as the causative pathogen. DISCUSSION: Successful repair was achieved surgically with a prosthetic bypass, followed by a 6-week course of intravenous antibiotics. Lifelong oral suppressant antibiotic treatment was then commenced. At 6-month follow up, the patient was free from clinical or radiological recurrence of infection or aneurysm. CONCLUSION: This case highlights an extremely rare aetiology for ruptured common iliac aneurysm in the form of Capnocytophaga canimorsus. It highlights the importance of a thorough history, including pet exposures, for patients with infected aneurysms and the need to ensure appropriate specimens are collected when a mycotic aneurysm is suspected.