A case report of mesenteric and portal vein thrombosis in a patient with Fusobacterium nucleatum bacteremia

Background: Fusobacterium bacteria are fastidious commensals in the human oropharyngeal microbiome. As pathogens, Fusobacterium are associated with diverse infectious and inflammatory conditions, including Lemierre's syndrome, colorectal cancer, and inflammatory bowel disease. Portal and mesenteric thromboses associated with Fusobacterium are case-reportable; due to the rarity of these reports, the full spectrum of presentations and outcomes remains unknown. Case presentation: A 71-year-old man presented with two weeks of abdominal pain and night sweats. He was found to have extensive portal and mesenteric venous thromboses and pancolitis. Initial workup for hypercoagulable risk factors was negative; after discharge, blood cultures became positive for Fusobacterium nucleatum. The patient was treated with antibiotics and anticoagulation with complete resolution of symptoms, thromboses, and colitis. Conclusions: This report demonstrates the protean nature of Fusobacterium-associated disease, which in this patient was portal and mesenteric venous thromboses without oropharyngeal disease. We discuss the modes of transmission, mechanisms of infection, and what remains unknown about the causes and consequences of Fusobacterium-associated disease. This report also demonstrates that cases with atypical abdominal thromboses, despite a negative comprehensive workup, deserve a high suspicion for other causal factors that are not part of standard diagnostic evaluation