Narrative review of autoantibodies in idiopathic inflammatory myopathies.

Objective: To discuss the characteristics of autoantigens, detection methods and roles of myositis associated autoantibodies (MAAs) and myositis specific autoantibodies (MSAs), as well as the clinical features of disease subgroups defined by MAAs/MSAs. Background: Autoantibodies in patients with idiopathic inflammatory myopathies (IIMs) are conventionally divided into MAAs and MSAs. MAAs usually refer to autoantibodies which are also available in systematic autoimmune diseases (anti-PM/SCL, anti-Ku, anti-Ro52 and anti-U1RNP antibodies). MSAs refer to autoantibodies which were distinctive for IIM (anti-Mi-2, anti-MDA5, anti-TIF1gammma, anti-NXP2, anti-SAE, anti-synthetase, anti-SRP, anti-HMGCR and anti-cN1A antibodies). The discovery and identification of novel autoantigens is a long and complicated process, which brought light in immunopathogenesis of IIMs. Detection methods of MAAs/MSAs mainly consist of monospecific methods [immunoprecipitation, enzyme-linked immune sorbent assay (ELISA) and indirect immunofluorescence] and multispecific methods [line immunoassay (LIA), dot immunoassay (DIA) and addressable laser bead assay (ALBIA)]. Patients with different MAAs/MSAs have different clinical features and require different clinical management. Methods: The search engine PubMed (https://www.ncbi.nlm.nih.gov/pmc/) was used to research the keywords "autoantibodies", "idiopathic inflammatory myopathies", "detection methods" and "clinical features". A narrative review was conducted to literature findings from 1975 to 2020. Conclusions: Development and validation of efficient detection methods of MAAs and MSAs help clinicians for diagnosis, classification and management of IIMs. The exploration of clinical features associated with different autoantibodies that facilitate the creation of diagnostic and classification guidelines and further clinical decision-making is of high value.