Dermatomyositis

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Background

  • Inflammatory myopathy
  • Affects proximal muscles > distal
  • Female:Male; 2:1
  • Peak incidence 40-50s

Clinical Features

Muscular

  1. Proximal greater than distal weakness
  • Deltoid and hip flexors
  • difficulty standing from a chair
  1. Onset over months
  2. Mild myalgias

Dermatologic

  1. Heliotrope rash on face scalp
  2. Gottron's papules (rash on MCP, PIP, and DIP joints)
  3. Shawl sign (rash above shoulders)

Other

  1. Cardiac (cardiomyopathy)
  2. High association with malignancy
  3. Interstial lung disease

Differential Diagnosis

Polymyositis SLE Guilanne Barre Syndrome Drug Induced Myopathies (Statins) Hypothyroidism Limb Girdle Muscular Dystrophy Rhabdomyositis Myesthenia gravis Pyomyositis Viral myositis Bolulism

Workup

  • CK
  • ANA
  • Chem for creatinine
  • Troponin, can involve myocardium
  • Bedside PFTs (FEV1 and FVC)
  • UA for myoglobin
  • Consider malignancies

Management

  • Severe disease: Respiratory muscle symptoms of CHF
    • Methylprednisolone 1000mg/day x 3 days
  • Mild disease: Prednisone 1mg/kg/day (up to 80mg/day)
    • Taper after 6-8 weeks

Disposition

  • Admit to monitored bed for CHF symptoms, respiratory muscle weakness
  • Admit for dysphagia/aspiration risk
  • Out patient follow up with muscle biopsy for others

See Also

Polymyositis SLE Rheumatoid arthritis


Sources

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