Pyogenic arthritis caused by Capnocytophaga gingivalis in an immunocompetent three-year-old male

Capnocytophaga gingivalis is most often isolated as normal oral flora or wi th periodontal disease. This organism is also associated with sepsis usuall y in immunocompromised hosts. We identified pyogenic arthritis caused by C. gingivalis in a 3-year-old immunocompetent male, whose clinical course clo sely resembled monoarticular onset pauciarticular juvenile rheumatoid arthr itis. This is the first report of C. gingivalis septic arthritis in the wor ld literature, but there are increasing reports of infections with this car bon dioxide-loving organism at other sites in nonimmunocompromised individu als. The subacute presentation of the monoarthritis with this organism of l ow virulence led to a long delay in diagnosis and treatment. Any monoarthri tis must continue to raise concern about infection.