Dermatomyositis: Myositis‐specific autoantibodies and skin manifestations

Idiopathic inflammatory myopathies including dermatomyositis ( DM ) and polymyositis ( PM ) are a heterogeneous group of disorders with varying degrees of muscle disease, cutaneous manifestations and internal organ involvement. Myositis‐specific autoantibodies ( MSA ) are useful tools, as they further define more homogeneous subsets. Anti‐ M i‐2 antibodies have been shown to represent a distinct DM phenotype with a low risk of interstitial lung disease ( ILD ) or cancer. Anti‐aminoacyl t RNA synthetase antibodies, such as anti‐ J o‐1, anti‐ PL ‐7, anti‐ PL ‐12, anti‐ EJ , anti‐ OJ and anti‐ KS antibodies, identify patients who share similar clinical features including ILD and myositis, which are referred to as “anti‐synthetase syndrome”. Anti‐155/140 antibodies and anti‐ CADM 140 antibodies have recently been described, and are considered as serological markers for cancer‐associated DM and clinically amyopathic DM with rapidly progressive ILD , respectively. In addition, recent studies have revealed anti‐ NXP ‐2 autoantibodies that are one of the predominant MSA in juvenile‐onset DM and anti‐small ubiquitin‐like modifier activating enzyme ( SAE ) antibodies that are also associated with a distinct phenotype. These autoantibodies are also associated with the distinct phenotype of skin manifestations. Thus, identification of the autoantibody profile in an individual patient is beneficial for management and therapy. Despite the clinical utility of MSA , these autoantibodies are unlikely to have direct pathogenic roles in the development of the disease. Findings suggest that the production of these antibodies reflects changes in autoantigen expression within the tissue targeted by the immune response. Furthermore, the nature of several autoantigens suggests their potential roles in tumor immunity and infection.