Idiopathic inflammatory myopathy
Last updated 22 Dec 2025
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Idiopathic inflammatory myopathy is a group of disorders characterised by inflammation of the muscles used for movement (skeletal muscles). Idiopathic inflammatory myopathy usually appears in adults between ages 40 and 60 or in children between ages 5 and 15, though it can occur at any age.
Description
Idiopathic inflammatory myopathy is a group of disorders characterised by inflammation of the muscles used for movement (skeletal muscles). Idiopathic inflammatory myopathy usually appears in adults between ages 40 and 60 or in children between ages 5 and 15, though it can occur at any age.
The primary symptom of idiopathic inflammatory myopathy is muscle weakness, which develops gradually over a period of weeks to months or even years. Other symptoms include joint pain and general tiredness (fatigue).
There are several forms of idiopathic inflammatory myopathy, including polymyositis, dermatomyositis, and sporadic inclusion body myositis.
Polymyositis and dermatomyositis involve weakness of the muscles closest to the center of the body (proximal muscles), such as the muscles of the hips and thighs, upper arms, and neck. People with these forms of idiopathic inflammatory myopathy may find it difficult to climb stairs, get up from a seated position, or lift items above their head. In some cases, muscle weakness may make swallowing or breathing difficult.
Polymyositis and dermatomyositis have similar symptoms, but dermatomyositis is distinguished by a reddish or purplish rash on the eyelids, elbows, knees, or knuckles. Sometimes, abnormal calcium deposits form hard, painful bumps under the skin (calcinosis).
In sporadic inclusion body myositis, the muscles most affected are those of the wrists and fingers and the front of the thigh. Affected individuals may frequently stumble while walking and find it difficult to grasp items. As in dermatomyositis and polymyositis, swallowing can be difficult.
Inheritance patterns
The source lists the following possible inheritance patterns: Pattern unknown. More than one pattern can apply in different cases.
Related genes
Other names
Idiopathic inflammatory myopathies
Idiopathic inflammatory myositis
Inflammatory myopathy, idiopathic
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Further reading and references
- Idiopathic inflammatory myopathy; MedlinePlus, National Library of Medicine.
- Chinoy H, Lamb JA, Ollier WE, Cooper RG. An update on the immunogenetics of idiopathic inflammatory myopathies: major histocompatibility complex and beyond. Curr Opin Rheumatol. 2009 Nov;21(6):588-93. doi: 10.1097/BOR.0b013e3283315a22.
- Chinoy H, Platt H, Lamb JA, Betteridge Z, Gunawardena H, Fertig N, Varsani H, Davidson J, Oddis CV, McHugh NJ, Wedderburn LR, Ollier WE, Cooper RG; UK Adult Onset Myositis Immunogenetic Collaboration and the Juvenile Dermatomyositis Research Group. The protein tyrosine phosphatase N22 gene is associated with juvenile and adult idiopathic inflammatory myopathy independent of the HLA 8.1 haplotype in British Caucasian patients. Arthritis Rheum. 2008 Oct;58(10):3247-54. doi: 10.1002/art.23900.
- Cox S, Limaye V, Hill C, Blumbergs P, Roberts-Thomson P. Idiopathic inflammatory myopathies: diagnostic criteria, classification and epidemiological features. Int J Rheum Dis. 2010 May;13(2):117-24. doi: 10.1111/j.1756-185X.2010.01472.x.
- O'Hanlon TP, Carrick DM, Arnett FC, Reveille JD, Carrington M, Gao X, Oddis CV, Morel PA, Malley JD, Malley K, Dreyfuss J, Shamim EA, Rider LG, Chanock SJ, Foster CB, Bunch T, Plotz PH, Love LA, Miller FW. Immunogenetic risk and protective factors for the idiopathic inflammatory myopathies: distinct HLA-A, -B, -Cw, -DRB1 and -DQA1 allelic profiles and motifs define clinicopathologic groups in caucasians. Medicine (Baltimore). 2005 Nov;84(6):338-349. doi: 10.1097/01.md.0000189818.63141.8c.
- Rider LG, Miller FW. Deciphering the clinical presentations, pathogenesis, and treatment of the idiopathic inflammatory myopathies. JAMA. 2011 Jan 12;305(2):183-90. doi: 10.1001/jama.2010.1977.
- Shamim EA, Miller FW. Familial autoimmunity and the idiopathic inflammatory myopathies. Curr Rheumatol Rep. 2000 Jun;2(3):201-11. doi: 10.1007/s11926-000-0080-0.
- Shamim EA, Rider LG, Miller FW. Update on the genetics of the idiopathic inflammatory myopathies. Curr Opin Rheumatol. 2000 Nov;12(6):482-91. doi: 10.1097/00002281-200011000-00002.
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