A limited number of case series has indicated that methotrexate (MTX) might be a useful drug in the treatment of dermatomyositis (DM), a rare autoimmune disease involving the skin and muscles. However, these earlier studies mainly focused on the efficacy of MTX on DM muscular symptoms. To analyse the efficacy of MTX on skin lesions in DM, the records of 34 patients with DM seen between 2004 and 2009 were retrospectively analysed, and the DM skin disease activity at different time points was determined, with specific focus on cutaneous features using the validated Cutaneous Dermatomyositis Activity Index (CDASI) score. The lesional inflammation was scored in primary skin biopsies. Additionally, we performed a systematic review of the available literature. In our series, 11 patients with DM received MTX, and in 8 of them, MTX led to a significant reduction of the DM skin lesions. CDASI scores decreased from 15.7 to 6.4 (P < 0.01) within 2-3 months, supporting the effectiveness of MTX in skin disease in DM. The lymphocytic infiltrate in primary skin lesions of MTX responders was significantly more pronounced than that in nonresponders. These results indicate that MTX might be an effective drug to treat the cutaneous symptoms of DM, as measured by the validated CDASI. Interestingly, MTX responders histologically presented a significantly stronger lesional lymphocytic inflammatory infiltrate than did nonresponders. These findings suggest that the functional inhibition of lymphocyte migration in the skin might be an important mechanism of MTX in the treatment of DM.
© The Author(s). CED © 2011 British Association of Dermatologists.