Mycobacterial Infections of Bones and Joints

Global rates of tuberculosis disease have declined in recent years because of improvements in case detection and expansion of treatment, but resistance to anti-tuberculous drugs remains a threat. Rheumatologists must remain vigilant for tuberculosis disease in an era of expanded use of TNF inhibitors and other biologic agents. Musculoskeletal tuberculosis is typically seen as a chronic localized infection, most commonly involving the spine and less often the hip or knee, but it can involve any joint. Rheumatologists should be particularly careful when treating atypical cases of subacute arthritis or tenosynovitis with local and systemic corticosteroids when infection with atypical pathogens, including mycobacteria, has not been ruled out. Diagnosis can be very difficult and often requires biopsy for histopathology and culture of the bone or synovium; nucleic acid amplification assays have demonstrated efficacy for rapid diagnosis of tuberculosis infection in bone and joint specimens. The tuberculin skin test (TST) can be helpful in identifying latent tuberculosis before treatment with TNF inhibitors, but it is limited by false-positive and false-negative results. Interferon-γ release assays appear to be similarly sensitive and even more specific than TSTs, but they can still produce both false-positive and false-negative test results. Treatment of active disease requires multiple agents selected on the basis of susceptibility testing for 6 to 9 months and has been complicated by drug resistance. Nontuberculous mycobacteria are important pathogens to recognize in the face of biologic therapy for rheumatic diseases.