Citation, DOI, disclosures and article data
Citation:
Sharma R, Idiopathic inflammatory myopathy. Reference article, Radiopaedia.org (Accessed on 31 Mar 2025) https://doi.org/10.53347/rID-190657
Disclosures:
At the time the article was last revised Henry Knipe had the following disclosures:
- Micro-X Ltd, Shareholder (past)
These were assessed during peer review and were determined to
not be relevant to the changes that were made.
View Henry Knipe's current disclosures
Idiopathic inflammatory myopathy is applied to a group of autoimmune inflammatory muscle disorders (myositis). Which specific disorders are included in this group has evolved, particularly with advances in the discovery of myositis-specific antibodies 1,2.
Diagnosis
The diagnosis of idiopathic inflammatory myopathies relies on symptoms, clinical examination, MRI findings, and biochemical results (e.g. muscle enzymes, autoantibodies) 5,6, although the gold standard is considered a histological diagnosis on muscle biopsy 6.
Pathology
There are several distinct conditions considered to be idiopathic inflammatory myopathies 1,2:
Additional suggested subtypes include 5
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, the term polymyositis is generally discouraged, and the existence of polymyositis as a standalone entity is a subject of conjecture 2,4.
Markers
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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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5. Lundberg I, Fujimoto M, Vencovsky J et al. Idiopathic Inflammatory Myopathies. Nat Rev Dis Primers. 2021;7(1):87. doi:10.1038/s41572-021-00325-7 - Pubmed
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6. Ashton C, Paramalingam S, Stevenson B, Brusch A, Needham M. Idiopathic Inflammatory Myopathies: A Review. Intern Med J. 2021;51(6):845-52. doi:10.1111/imj.15358 - Pubmed
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