Last reviewed: November 2017
Last updated: November  2017

Summary

Definition

History and exam

Key diagnostic factors

  • presence of risk factors
  • difficulty with motor tasks
  • muscle weakness
  • heliotrope rash with eyelid oedema
  • Gottron's papules
  • muscle atrophy

Other diagnostic factors

  • frequent falls
  • fatigue and generalised malaise
  • weight loss
  • shortness of breath
  • mild fever
  • abnormal breath sounds
  • dysphagia
  • myalgia
  • arthralgia
  • palpitations
  • syncope
  • symptoms of MI
  • facial rash
  • erythematous rash
  • nail fold changes
  • facial muscle weakness
  • skin calcinosis
  • joint swelling
  • arrhythmias
  • signs of heart failure and/or MI
  • physical findings of malignancy
  • systemic signs of autoimmune disease
  • peripheral neuropathy

Risk factors

  • children and 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)
  • non-viral infection
  • vaccination
  • D-penicillamine
  • other drugs or toxins

Diagnostic investigations

1st investigations to order

  • CK
  • EMG
  • muscle biopsy
  • aldolase
  • LDH
  • alanine transaminases
  • myoglobin
Full details

Investigations to consider

  • ESR
  • ANA
  • myositis-specific antibodies
Full details

Emerging tests

  • soluble CD30
  • type 1 interferon
  • MRI
  • ultrasound scan
Full details

Treatment algorithm

Contributors

Authors VIEW ALL

Associate Professor of Neurology

Rutgers, The State University of New Jersey

New Jersey Medical School

Newark

NJ

Disclosures

NS declares that he has no competing interests.

Peer reviewers VIEW ALL

Physician

Department of Neurology

Penn Presbyterian Medical Center

University of Pennsylvania Health System

Philadelphia

PA

Disclosures

SK declares that he has no competing interests.

Vice-Chairman

Department of Neurology

Brigham and Women's Hospital

Harvard Medical School

Boston

MA

Disclosures

AAA declares that he has no competing interests.

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