2018 Volume 30 Issue 3 Pages 145-153
Idiopathic inflammatory myopathy（IIM）refers to heterogenous disorders that manifest mainly muscle weakness and myalgia due to inflammation of muscles. IIM is classified into largely three diseases; polymyositis（PM）, dermatomyositis（DM）and inclusion body myositis（IBM）. Previous studies revealed that autoantibodies directed against nuclear or cellular components are detected in patients with IIM. Most of these autoantibodies are found exclusively in patients with this condition and are called myositis-specific antibodies（MSAs）. Antibodies against aminoacyl tRNA synthetases（ARS）such as anti-Jo-1 antibody, signal recognition particle（SRP）or Mi-2 have been found at an early stage and are well-established PM/DM specific antibodies. Since 2000, additional autoantibodies specific for IIM have been discovered and reported by several investigators. These novel MSAs, with few exceptions, have proven useful for precise diagnosis, treatment selection, prognosis prediction, and classification of IIM patients into clinical entity. Especially, anti-TIF1-γ antibody and anti-MDA5 antibody are clinically important because the former is assosiated with cancer-associated myositis and the latter is detected in DM with rapidly progressive interstitial lung disease. This article reviews autoantibodies detected in patients with IIM as well as the association between these MSAs and clinical characteristics and immunological findings to classify IIM patients into distinct clinical subsets.
