[Autoantibodies specifically detected in patients with polymyositis/dermatomyositis]

Polymyositis/Dermatomyositis (PM/DM) is a chronic inflammatory disorder that culminates in injury to the skin and muscle and, sometimes, is accompanied by interstitial lung disease (ILD). A number of autoantibodies are associated with myositis, including those specific for aminoacyl-tRNA synthetase (anti-ARS), signal recognition particle (anti-SRP), and Mi-2. These autoantibodies have proven to be useful in the diagnosis and classification of the diseases and are predictive of prognosis. It has been known that certain patients may have typical DM skin manifestations without clinical evidence of myositis for at least 2 years (Clinically Amyopathic DM; C-ADM). Although classical myositis-related antibodies are well known, specificities related to C-ADM have not been examined in detail. Therefore, we have examined sera from 15 Japanese patients with C-ADM to identify additional autoantibodies associated with this disease. Eight sera of C-ADM patient recognized a polypeptide of approximately 140 kDa and we named this new antibody specificity anti-CADM-140. Anti-CADM-140 antibodies were detected in 8 of 42 patients with DM, but not in patients with other connective tissue diseases or idiopathic pulmonary fibrosis. It is noteworthy that DM patients with anti-CADM-140 had significantly more rapidly progressive ILD when compared to patients without anti-CADM-140 (50% vs 6%, P=0.008). Further studies of the pathogenicity of these autoantibodies specificity may provide insight into the pathogenic mechanisms of PM/DM accompanied by rapidly progressive ILD.