Polymyositis (PM) is found mostly in people over the age of 20 and affects more women than men. Muscle weakness usually happens over days, weeks or months. The weakness begins with muscles closest to and within the trunk of the body. Neck, hip, back and shoulder muscles are examples. Some patients also have weakness in muscles farther from the trunk, like hands and fingers. Some PM patients experience muscle pain, breathing problems, and trouble swallowing.

Researchers are finding that each case of PM is quite different from others. Sometimes, cases originally diagnosed as PM and not responding to treatment are later found to be inclusion-body myositis (IBM). Patients with certain types of PM may have one or more other autoimmune diseases.

Signs and symptoms


  • Sudden or gradual weakness in the muscles
  • Difficulty swallowing (dysphagia)
  • Falling and difficulty getting up from a fall
  • General feelings of tiredness
  • Chronic dry cough


  • Marked weakness in the muscles closest to the center of the body, like the forearms, thighs, hips, shoulders, neck and back
  • Sometimes, weakness in the fingers and toes
  • Thickening of the skin on the hands (mechanic's hands)



Updated March 2012




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