Septic arthritis followed by reactive arthritis due to Yersinia enterocolitica in an eight-year-old boy.

An eight-year-old boy admitted for a limp on the left side was found to have septic arthritis of the left knee due to Yersinia enterocolitica. The symptoms improved under antimicrobial therapy, but inflammatory arthritis responsive to diclofenac developed subsequently in the same joint, The succession of septic and reactive arthritis in the same joint is highly unusual, Conventional microagglutination or microplate serologic tests for Y. enterocolitica can yield false-negative results, whereas ELISA testing is highly reliable.