Tuberculosis diagnosed by PCR analysis of synovial fluid.

Tuberculosis is a leading cause of mortality due to an infectious agent worldwide. It often affects multiple organs by hematogenous spread of Mycobacterium tuberculosis, but knee-joint involvement is extremely rare, comprising approximately 0.1% of all forms of tuberculosis. We present a case of tuberculous pleuritis with knee-joint involvement. Cytological and biochemical analysis of the pleural fluid and a biopsy specimen of the cervical lymph node indicated tuberculosis, but a definitive diagnosis was not given. A confirmed diagnosis was finally obtained through PCR analysis of the synovial fluid. Tuberculosis should be included in the differential diagnosis in patients with persistent pain and swelling of the knee. PCR analysis of the synovial fluid is a quick and useful method for the diagnosis.