How is polymyositis characterized?

Updated: Feb 12, 2018
  • Author: Mythili Seetharaman, MD; Chief Editor: Herbert S Diamond, MD  more...
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Answer

Polymyositis is an idiopathic inflammatory myopathy characterized by the following [1] :

  • Symmetrical, proximal muscle weakness
  • Elevated skeletal muscle enzyme levels
  • Characteristic electromyography (EMG) and muscle biopsy findings (see the images below).
MRI of thighs showing increased signal in the quad MRI of thighs showing increased signal in the quadriceps muscles bilaterally consistent with inflammatory myositis.
Histopathology of polymyositis showing endomysial Histopathology of polymyositis showing endomysial mononuclear inflammatory infiltrate and muscle fiber necrosis.

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