Polymyositis (PM) is thought to be an autoimmune disease where inflammation resulting in cell damage is created when the immune system attacks healthy muscle tissue.

Muscle weakness can develop over a period of days, weeks, or months, is typically symmetrical (both sides of the body), and affects proximal muscles (muscles which are closest to the body’s core), such as the quadriceps, hip flexors, neck, and deltoid muscles.  It affects and weakens the skeletal muscles, those involved with voluntary movement. This weakness often leads to difficulty climbing stairs, rising from a chair or the floor, turning in bed, lifting, styling hair, or reaching over the head for something like an item on a shelf.  Some people also have problems swallowing, a disorder called “Dysphagia.”  Muscle pain (myalgia) and joint pain, with or without true arthritis and joint inflammation, can also be a part of PM.

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