Cutaneous infection due to Mycobacterium chelonae during anti-TNF therapy

Mycobacterium chelonae is a ubiquitous, rapidly growing, opportunistic, non-tuberculous mycobacterium that can cause skin and bone tissue infections. We report a case of cutaneous infection due to M. chelonae following anti-TNF therapy. A 70-year-old woman with a medical history of rheumatoid arthritis was admitted for several purple nodular cutaneous lesions on her right leg evolving for 2 months. At admission, she was on prednisone, methotrexate and adalimumab for her rheumatoid arthritis. Skin lesions appeared 5 days before etanercept, which was taken for 5 months before being discontinued for adalimumab. Both the histopathological examination and bacterial culture of involved skin showed the presence of M. chelonae. Adalimumab was immediately discontinued and a combination of amoxicillin-clavulanic acid and tigecyclin was started. TNF-alpha plays a pivotal role in immune reaction to intracellular pathogens. Very few cases of cutaneous infection involving M. chelonae in association with an anti-TNF-alpha therapy have been reported in the literature. To our knowledge, this is the first case occurring during treatment with etanercept and symptoms worsened with the introduction of adalimumab. In addition, this case underlines the difficulties of effectively treating this mycobacterium.