Reactive arthritis in connective tissue diseases; one should be vigilant for joint tuberculosis.

The incidence of tuberculosis (TB) is increasing worldwide. Bone and joint TB are the most common types of extra-pulmonary TB, but can easily be misdiagnosed, since articular TB commonly mimics other joint diseases, including reactive and degenerative arthritis, and articular manifestations associated with systemic autoimmune diseases. Furthermore, patients with systemic auto-immune diseases are often more prone to mycobacterial infection. The diagnosis of joint TB can be made using a combination of the following methods: clinical evaluation, imaging, tuberculin skin test, interferon-gamma release assays, nucleic acid amplification tests, and Gene X-pert MTB/rifampicin assay.