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
- shortness of breath
- mild fever
- abnormal breath sounds
- dysphagia
- myalgia
- arthralgia
- palpitations
- syncope
- facial rash
- erythematous rash
- nail fold changes
- facial muscle weakness
- skin calcinosis
- joint swelling
- arrhythmias
- signs of heart failure and/or myocardial infarction
- physical findings of malignancy
- systemic signs of autoimmune disease
- peripheral neuropathy
Risk factors
- age >40 years
- exposure to high intensity of global UV radiation
- genetic predisposition
- female sex and/or black ethnicity (polymyositis and dermatomyositis)
- male sex and/or white ethnicity (inclusion body myositis)
- lipid-lowering agents
- HIV
- viral infections (excluding HIV)
- nonviral infection
- vaccination
- D-penicillamine
- other drugs or toxins
Diagnostic investigations
1st investigations to order
- creatine kinase
- electromyograph
- muscle biopsy
- myositis-specific and associated autoantibodies
- magnetic resonance imaging
- aldolase
- lactate dehydrogenase
- alanine aminotransferase
- aspartate aminotransferase
- myoglobin
Investigations to consider
- erythrocyte sedimentation rate
- C-reactive protein
- antinuclear antibodies
- serum creatinine
- serum ferritin
- fluorodeoxyglucose positron emission tomography (FDG-PET)/computed tomography
Emerging tests
- ultrasound scan
Treatment algorithm
induction of remission: with severe muscle weakness or life-threatening complications
induction of remission: without severe muscle weakness or life-threatening complications
maintenance of remission: 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 advisory board/lecture fees from Lilly, UCB, Janssen, and Biogen; has done consultancy work for Novartis and Momenta; has received travel expenses from Abbvie, Janssen, and Eli Lilly; and has received research grants from UCB and MedImmune. He is also an author of several references cited in this topic.
James Lilleker, PhD, MBChB
Clinical Lecturer in Neurology
Centre for Musculoskeletal Research
Division of Musculoskeletal and Dermatological Sciences
The University of Manchester
Manchester
Neurology Registrar
Manchester Centre for Clinical Neuroscience
Salford Royal NHS Foundation Trust
Manchester Academic Health Sciences Centre
Salford
UK
Disclosures
JL is an author of several references cited in this topic.
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
Sami Khella, MD
Physician
Department of Neurology
Penn Presbyterian Medical Center
University of Pennsylvania Health System
Philadelphia
PA
Disclosures
SK declares that he has no competing interests.
Anthony Arnold Amato, MD
Vice-Chairman
Department of Neurology
Brigham and Women's Hospital
Harvard Medical School
Boston
MA
Disclosures
AAA declares that he has no competing interests.
Differentials
- Hereditary inclusion body myositis
- Oculopharyngeal muscular dystrophy
- Late-onset distal myopathy
More DifferentialsGuidelines
- Guideline for vaccinations in patients with rheumatic and musculoskeletal diseases
- EFNS guidelines for the use of intravenous immunoglobulin in treatment of neurological diseases
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