Summary
Definition
History and exam
Key diagnostic factors
- difficulty with motor tasks
- muscle weakness
- muscle atrophy
- heliotrope rash with eyelid edema
- Gottron papules
Other diagnostic factors
- frequent falls
- fatigue and generalized malaise
- weight loss
- signs of heart failure and/or myocardial infarction, arrhythmias, shortness of breath, abnormal breath sounds, palpitations, syncope
- mild fever
- dysphagia
- myalgia
- arthralgia and/or swollen joint
- facial rash
- erythematous rash
- nail fold changes
- facial muscle weakness
- skin calcinosis
- malignancy
- systemic signs of autoimmune disease
- Raynaud phenomenon
Risk factors
- age >40 years
- genetic predisposition
- female sex and/or black ethnicity (polymyositis and dermatomyositis)
- male sex and/or white ethnicity (inclusion body myositis)
- use of statins
- tobacco smoking
- exposure to high intensity of global UV radiation
- infections
- vaccination
- use of certain drugs
- other environmental factors
Diagnostic tests
1st tests to order
- creatine kinase
- electromyograph
- muscle biopsy
- myositis-specific and associated autoantibodies
- magnetic resonance imaging
- aldolase
- lactate dehydrogenase
- alanine aminotransferase
- aspartate aminotransferase
- myoglobin
Tests to consider
- erythrocyte sedimentation rate
- C-reactive protein
- antinuclear antibodies
- serum creatinine
- high resolution computed tomography of the lungs
- pulmonary function test
- diffusion capacity
- serum ferritin
- troponins
- electrocardiography
- echocardiography
- cardiac magnetic resonance imaging
- fluorodeoxyglucose positron emission tomography (FDG-PET)/computed tomography
- muscle ultrasound scan
Treatment algorithm
severe idiopathic inflammatory myopathies: initial presentation
nonsevere idiopathic inflammatory myopathies: initial presentation
remission achieved: any severity
Contributors
Authors
Hector Chinoy, PhD, FRCP, BMBS, MSc, BMedSci
Professor of Rheumatology and Neuromuscular Disease
National Institute for Health Research Manchester Biomedical Research Centre
Manchester University NHS Foundation Trust
The University of Manchester
Manchester
UK
Disclosures
HC has received grant support from Eli Lilly and UCB; consulting fees from Novartis, Eli Lilly, Orphazyme, AstraZeneca, Pfizer, Kezar Life Science; speaker for UCB and Biogen. He is also an author of several references cited in this topic.
James Lilleker, PhD, MBChB
Consultant Neurologist and Honorary Senior Lecturer
Muscle Disease Unit
Salford Royal Hospital Manchester
Centre for Clinical Neurosciences
Salford
Centre for Musculoskeletal Research
Division of Musculoskeletal and Dermatological Sciences
University of Manchester
Manchester
UK
Disclosures
JL has been reimbursed by Roche for consultancy, received sponsored travel and accommodation conference support from Roche, and is on the speakers’ bureau for Sanofi, and is an author of several references cited in this topic.
Choon Guan Chua, MBBS, MRCP (UK), DAvMed (UK), FRCP
Consultant Rheumatologist
Department of Rheumatology, Allergy, and Immunology
Tan Tock Seng Hospital
Singapore
Disclosures
CGC declares that he has no competing interests.
Acknowledgements
Dr Hector Chinoy and Dr James Lilleker would like to gratefully acknowledge Dr Nizar Souayah, the previous contributor to this topic.
Disclosures
NS declares that he has no competing interests.
Peer reviewers
Hani Kushlaf, MD
Associate Professor of Neurology & Pathology
Director of Neuromuscular Research
University of Cincinnati
College of Medicine
Cincinnati
OH
Disclosures
HK has served as a consultant on advisory boards for Alexion AstraZeneca Rare Disease, Argenx, Catalyst, Sanofi, Takeda, Immunovant, and UCB. HS has served for the speaker bureau of Sanofi.
References
Key articles
Lundberg IE, Fujimoto M, Vencovsky J, et al. Idiopathic inflammatory myopathies. Nat Rev Dis Primers. 2021 Dec 2;7(1):86. Abstract
Schmidt J. Current classification and management of inflammatory myopathies. J Neuromuscul Dis. 2018;5(2):109-29.Full text Abstract
Oldroyd A, Lilleker J, Chinoy H. Idiopathic inflammatory myopathies: a guide to subtypes, diagnostic approach and treatment. Clin Med (Lond). 2017 Jul;17(4):322-8.Full text Abstract
Oldroyd AGS, Lilleker JB, Amin T, et al. British Society for Rheumatology guideline on management of paediatric, adolescent and adult patients with idiopathic inflammatory myopathy. Rheumatology (Oxford). 2022 May 5;61(5):1760-8.Full text Abstract
Reference articles
A full list of sources referenced in this topic is available to users with access to all of BMJ Best Practice.
Differentials
- Hereditary inclusion body myositis
- Oculopharyngeal muscular dystrophy
- Late-onset distal myopathy
More DifferentialsGuidelines
- Guideline for vaccinations in patients with rheumatic and musculoskeletal diseases
- Guideline for idiopathic inflammatory myopathy-associated cancer screening
More Guidelines
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