Capnocytophaga canimorsus-Induced Sepsis Unmasking an Aortic Aneurysm: A Case Report.

Capnocytophaga canimorsus is a gram-negative, anaerobic bacillus commonly found in the oral flora of dogs and cats. While often transmitted through animal bites or scratches, severe infections can occur even without documented exposure, particularly in immunocompromised individuals such as asplenic patients. Although rare, mycotic aneurysms caused by C. canimorsus are associated with high mortality. We report the case of a 53-year-old male with a history of splenectomy due to diffuse large B-cell lymphoma, currently in remission, who presented with malaise, fever, dyspnea, and abdominal pain. He rapidly progressed to septic shock and multiorgan failure, including coagulopathy consistent with disseminated intravascular coagulation (DIC). Despite broad-spectrum antibiotics and intensive support, the patient died within hours of admission. Blood cultures later confirmed C. canimorsus bacteremia. Postmortem examination revealed a ruptured aortic aneurysm. This case highlights the fulminant progression of C. canimorsus infection in an asplenic patient, culminating in a fatal aortic aneurysm rupture. Notably, there was no history of animal exposure, reinforcing the need for high clinical suspicion, especially in high-risk populations. Although empiric therapy with beta-lactam/beta-lactamase inhibitors is recommended, early recognition and possible surgical intervention remain crucial for survival. Infections caused by C. canimorsus should be considered in septic patients with risk factors such as splenectomy, even in the absence of animal contact. Rapid deterioration and rare complications, like aortic aneurysm rupture, underscore the importance of early diagnosis and aggressive multidisciplinary management.