Polymyositis

• Facts:
  Immune mediated striated muscle inflammation
  Progressive, systemic connective tissue disease
  
• History / PE:
  Symmetric, progressive proximal muscle weakness
  Pain, weakness
  Difficulty breathing or swallowing
  
• Diagnosis:
  Increase serum CK, ESR
  Anti-Jo-1 antibodies
  Inflammation, necrosis, and regeneration (muscle biopsy)
• Treatment:
  High dose corticosteroids (taper 4-6wks to maintenace dose)
  Azathioprine and/or methotrexate
• Associated With:
  Underlying malignancy (especially breast and lung CA)
  Myocarditis
  Cardiac conduction deficits
• Differential Diagnosis:
  Dermatomyositis
  Inclusion body myositis
  Drug induced myopathy (eg. statins , antipsychotics)
  Steroid-induced myopathy
  Myasthenia gravis
  Thyroid myopathy