Polymyositis Evaluation

Erythrocyte Sedimentation Rate (ESR)
1. Increased in 50% of cases
2. Poor correlation with disease activity
Rheumatoid Factor
1. Increased in 20% of cases
2. Associated with overlap syndrome
Antinuclear Antibody (ANA)
1. Seen in 80% of Dermatomyositis and Polymyositis patients

Anti-Jo1
1. Seen in 20% of Dermatomyositis
Anti-EJ
1. Associated with Dermatomyositis
Signal Recognition Particle (SRP)
1. Seen in 5% of Polymyositis
2. Associated in severe, acute-onset Polymyositis
  1. Treatment resistant Dermatomyositis, Polymyositis
  2. Associated with cardiac involvement
Anti-Mi2
1. Seen in 15-20% of classic Dermatomyositis
2. Associated conditions
  1. Treatment-responsive form
  2. Shawl sign in Dermatomyositis
  3. Prominent cuticular changes
Anti-PM-Scl
1. Seen in overlap syndrome
2. Associated conditions
  1. Dermatomyositis and Polymyositis
  2. Scleroderma
Anti-Ku
1. Seen in overlap syndrome
2. Associated conditions

False Negative in 10% of cases
Myopathic or myogenic pattern
1. Short duration, polyphasic motor unit potentials
2. Spontaneous fibrillation potentials

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