Citation, DOI, disclosures and article data
Citation:
Sharma R, Idiopathic inflammatory myopathy. Reference article, Radiopaedia.org (Accessed on 15 Mar 2025) https://doi.org/10.53347/rID-190657
Idiopathic inflammatory myopathy (IIM) is a term applied to a group of autoimmune inflammatory muscle disorders (myositis). Which specific disorders are included in this group has evolved over time, in particular with advances in discovery of myositis-specific antibodies 1,2.
Classification
There are four distinct conditions considered to be idiopathic inflammatory myopathies 1,2:
Polymyositis was historically classified as an idiopathic inflammatory myopathy 3, however, many patients given this diagnosis occurred before many myositis-specific antibodies were discovered, and subsequent research of these historical cases has shown that many cases would be re-classified as other idiopathic inflammatory myopathies 1. Thus, use of the term polymyositis is generally discouraged, and the existence of polymyositis as a standalone entity is a subject of conjecture 2,4.
See also
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1. Mariampillai K, Granger B, Amelin D et al. Development of a New Classification System for Idiopathic Inflammatory Myopathies Based on Clinical Manifestations and Myositis-Specific Autoantibodies. JAMA Neurol. 2018;75(12):1528-37. doi:10.1001/jamaneurol.2018.2598 - Pubmed
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2. Tanboon J, Uruha A, Stenzel W, Nishino I. Where Are We Moving in the Classification of Idiopathic Inflammatory Myopathies? Curr Opin Neurol. 2020;33(5):590-603. doi:10.1097/wco.0000000000000855 - Pubmed
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3. Bottai M, Tjärnlund A, Santoni G et al. EULAR/ACR Classification Criteria for Adult and Juvenile Idiopathic Inflammatory Myopathies and Their Major Subgroups: A Methodology Report. RMD Open. 2017;3(2):e000507. doi:10.1136/rmdopen-2017-000507 - Pubmed
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4. Leclair V, Notarnicola A, Vencovsky J, Lundberg I. Polymyositis: Does It Really Exist as a Distinct Clinical Subset? Curr Opin Rheumatol. 2021;33(6):537-43. doi:10.1097/BOR.0000000000000837 - Pubmed
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