Capnocytophaga canimorsus sepsis in a methotrexate-treated patient with rheumatoid arthritis

Abstract

Capnocytophaga canimorsus is a gram-negative rod that can be transmitted primarily by dog bites. This life-threatening organism commonly causes sepsis in patients with splenectomy or alcoholism. A 53-year-old rheumatoid arthritis male treated with methotrexate (MTX) for 5 years was admitted for a 4-day history of fever and dyspnea. He had been bitten on a finger by the family dog 4 days before onset. Laboratory tests revealed pancytopenia, acute renal failure, and evidence of disseminated intravascular coagulation, and he subsequently developed acute respiratory distress syndrome. Furthermore, blood cultures grew gram-negative bacilli and despite intensive treatment, he died 5 days after admission. Later, C. canimorsus was identified from his culture samples using a species-specific polymerase chain reaction. C. canimorsus infections should be considered in the differential diagnosis of sepsis for immunocompromised hosts following animal bites.

Keywords: Capnocytophaga canimorsus; Iatrogenic immunocompromised hosts; Methotrexate; Rheumatoid arthritis; Sepsis.

Fig. 1

Index finger of the patient showing a wound from a dog bite without cellulitis and erythema.

Fig. 2

Chest simple computed tomography at the time of admission (A) and after transfer to ICU (B).

Fig. 3

Microscopic images of Giemsa staining of the peripheral blood smear from the patient, which show some slender rods in the cytoplasm of the neutrophils.