<i>Mycobacterium kansasii</i> tenosynovitis in a rheumatoid arthritis patient with long‐term therapeutic immunosuppression

Abstract

Introduction Atypical or nontuberculous mycobacteria are normal commensals of water, soil, dust, and cattle milk. Human infections are relatively uncommon, but an increasing number of cases have been reported in the context of human immunodeficiency virus (HIV) or therapeutic immunosuppression (1). Mycobacterium avium complex and Mycobacterium kansasii account for most episodes of nontuberculous systemic diseases. Besides many reports of patients with HIV, there are only rare published examples of patients with chronic inflammatory arthritides under immunosuppression therapy. Most of these reports describe Mycobacterium marinum infections (2–4). In the last 7 years, there have been only a few reports of M kansasii infections in patients with chronic inflammatory rheumatic diseases (5–11). Nakamura et al (8) collected references on 11 patients from the literature since 1963. Bernard et al (9) described a French retrospective study of 26 patients from their own clinic and the literature who had M kansasii septic arthritis and no underlying disease. This indicates that, overall, this infectious complication is very rare. However, the incidence might increase as we tend to use more aggressive immunosuppressants (especially tumor necrosis factor inhibitors) with a more relevant impact on the immune system. Moreover, with better diagnostic possibilities and better awareness of the necessity of an aggressive treatment, immunosuppression therapy will start much earlier. We report a patient with long-lasting seronegative rheumatoid arthritis and a more recent local tenosynovitis. We identified a local M kansasii infection as the cause for the tenosynovitis on the basis of a positive bacterial culture result. AlthoughM kansasii is second only toM avium complex as the causative agent of nontuberculous lung disease, which often involves the upper lobe, it is rarely identified as a cause of extrapulmonary infection, especially arthritis or tenosynovitis. The infection primarily infects the lungs with rare precipitation in joints, tendons, or bone (9,12). When affecting the joints, monarthritis is usually erosive (11,13). Infections with M kansasii are environmentally acquired. It has been isolated from tap water in the warm southern US states (Texas), where it can survive for up to 12 months (14,15).