Role of environmental factors in autoantibody production - importance of a detailed analysis in a small cohort.

In the previous issue of Arthritis Research & Therapy, Muro and colleagues reported a detailed epidemiologic analysis in central Japan on one of the new myositis-specific autoantibodies to MDA-5 (melanoma differentiation-associated gene 5), which is associated with clinically amyopathic dermatomyositis accompanying interstitial lung disease. The increasing prevalence of anti-MDA-5, higher prevalence in small rural towns, and geographical clustering in two areas along the Kiso River suggest a role of environmental factors associated with rural communities or the river/water system or both. A detailed analysis of a small cohort may offer clues, which is ignored in multi-center studies, to the pathogenesis of systemic rheumatic diseases and autoantibody production.