Abstract
Purpose of reviewTo review the advances that have been made in our understanding of the genetics of idiopathic inflammatory myopathies (IIM) in the past 2 years, with a particular focus on dermatomyositis and polymyositis.Recent findingsFine-mapping studies in the major histocompatibility complex region in Caucasian and Korean populations have identified novel human leukocyte antigen (HLA) variants that are associated with autoantibody subgroups in IIM. Differences in HLA associations have been identified between Caucasian adult-onset and juvenile-onset patients with anti-TIF1 autoantibodies, suggesting distinct aetiologies in these patients. For some autoantibodies, the strongest associations identified are specific amino acid positions within HLA molecules, providing mechanistic insights into disease pathogenesis.A meta-analysis combining data from four seropositive rheumatic diseases identified 22 novel non-HLA associations in IIM, of which seven were previously reported at suggestive significance in IIM. A genome-wide association study conducted in the Japanese population identified a significant association with WDFY4 in patients with clinically amyopathic dermatomyositis.SummaryConsiderable progress has been made in understanding the genetics of IIM, including differences in clinical and autoantibody subgroups. As research continues, there should be a focus to increase statistical strength and precision by conducting meta-analyses and trans-ethnic studies.
Highlights
The idiopathic inflammatory myopathies (IIM), collectively known as myositis, are a group of rare autoimmune diseases
Significant progress has been recently made in studying the genetics of IIM, and we are beginning to understand more about the genetic architecture of these rare diseases
The most common autoantibody in this study was anti-MDA5 in 26.8% of patients tested (n 1⁄4 48), and a strong association was reported with human leukocyte antigen (HLA)-DRB1Ã12 : 02 (Pcorr 1⁄4 0.001; OR 1⁄4 5.46; 95% CI, 2.67–11.20)
Summary
The idiopathic inflammatory myopathies (IIM), collectively known as myositis, are a group of rare autoimmune diseases. They are characterized primarily by skeletal muscle weakness and muscle inflammation, and commonly present with extramuscular manifestations such as skin rash, interstitial lung disease, polyarthritis and cancer. ACentre for Musculoskeletal Research, Faculty of Biology, Medicine and Health, bNational Institute for Health Research Manchester Biomedical Research Centre, Manchester University NHS Foundation Trust, University of Manchester, Manchester, cRheumatology Department, Salford Royal NHS Foundation Trust, Manchester Academic Health Science Centre, Salford and dDivision of Population Health, Health Services Research & Primary Care, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
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