[Multiple erythema annulare centrifugum associated with knee monoarthritis revealing Capnocytophagacanimorsus infection].

Introduction: Capnocytophagacanimorsus (C. canimorsus), a commensal Gram-negative bacillus found in the oral cavity of dogs and cats, is pathogenic for humans, with the most common clinical manifestations being septicemia, meningitis and endocarditis. Herein we report a case of CC bacteremia manifesting as multiple plaques of erythema annulare centrifugum associated with monoarthritis of the knee.
Patients and Methods: A 66-year-old man consulted for a skin rash and monoarthritis of the right knee with fever following an insect bite on his right hallux. Cutaneous examination revealed numerous erythematous annular plaques on the trunk and limbs with centrifugal extension. Analysis of synovial fluid from the right knee showed an inflammatory liquid with a sterile bacteriological culture and PCR was negative for Borrelia. C. canimorsus bacteria were isolated from blood cultures. 16S RNA PCR performed on the synovial fluid was positive for the same organism. The patient's history revealed that his hallux wound had been licked by his dog.
Discussion: C. canimorsus most frequently affects immunosuppressed subjects. Cutaneous signs are seen in half of all cases, most frequently presenting as cellulitis, pathological livedo or thrombotic purpura. We report herein a case of CC bacteremia in an immunocompetent patient manifesting as multiple plaques of erythema annulare centrifugum, an unusual sign, and monoarthritis of one knee.
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