Mycobacterium kansasii causing septic arthritis and osteomyelitis in a child.

We present the case of a boy with a 3-year history of relapsing/remitting monoarthritis of the ankle joint. Despite negative cultures at first presentation, synovial fluid examination revealed Mycobacterium kansasii. This is the youngest reported case of M. kansasii septic arthritis in a child.