What is "polymyositis"

n. (context medicine English) An inflammatory disease affecting multiple muscles

n. myositis characterixed by weakness of limb and neck muscles and much muscle pain and swelling; progression and severity vary among individuals

Polymyositis (PM) ("inflammation of many muscles") is a type of chronic inflammation of the muscles ( inflammatory myopathy) related to dermatomyositis and inclusion body myositis. The inflammation is predominantly of the endomysium in polymyositis, whereas dermatomyositis is characterized by primarily perimysial inflammation.