A case of clinically amyopathic dermatomyositis that developed during anti-TNF-α therapy for rheumatoid arthritis

Dear Editor, Clinically amyopathic dermatomyositis (CADM) in association with rapidly progressive interstitial pneumonia (RP-ILD) has a high mortality rate. Although the pathogenesis of CADM is not clear, interferon and interferon-induced molecules are related to the onset and activity of dermatomyositis and myositis. Anti-tumor necrosis factor alpha (TNF-α) is now widely used for the treatment of autoimmune diseases, such as rheumatoid arthritis, inflammatory bowel diseases, psoriasis, and vasculitis. However, the development of autoimmune diseases, including dermatomyositis/polymyositis, has been reported during anti-TNF-α-treatment. In addition, interferon-α has been shown to be increased during anti-TNF-α-treatment. In this letter, we describe a case of newly onset CADM during etanercept (an anti-TNF-α drug) therapy, which was successfully treated with multi-target therapy using steroids, cyclophosphamide, and tacrolimus. A 52-year-old female with a 15-year history of rheumatoid arthritis was referred to our department with a cough, general fatigue, arthritis affecting multiple joints, and skin eruption.