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Polymyositis is a rare disease of the muscles. It makes muscles inflamed or swollen. It can lead to severe movement problems. Treatment can help.

Front Muscles of Trunk
Trunk Core Muscles
Copyright © Nucleus Medical Media, Inc.


Changes in genes may be the cause. The altered genes change how your immune system responds to the environment. It leads to attack of muscles by the immune system.

Risk Factors

Polymyositis is more common in:

  • Women
  • People who are 30 to 50 years old

Your risk is higher if people in your family have lupus .


The muscles near the trunk of the body are affected more often. You may have:

  • Poor muscle strength in the hips, neck, and shoulders
  • Muscle pain that gets worse over time
  • Low energy
  • Great effort needed to climb stairs
  • Trouble rising from a chair
  • Problems reaching above your head
  • Having a dry cough that won’t go away
  • A hard time when you swallow

Polymyositis can also lead to:


You will be asked about your symptoms and health history. A physical exam will be done.

The following tests may be done to confirm muscle disease:

  • Blood tests—to look for signs of muscle breakdown
  • Muscle biopsy —to look for inflammation or damage
  • Electromyogram (EMG)—test electrical activity of the muscle
  • MRI —can show large areas of inflammation


The disease starts slowly and gets worse over time. There is no cure. The muscles will get weaker and more painful without treatment.

Medical care can help with your strength and movement. Some treatment options include:


Medicine will depend on your specific needs. Options include:

  • Corticosteroids—to reduce inflammation
  • Other immunosuppressants—to decrease damage caused by immune system
  • IV immunoglobulin therapy —special proteins that may help the immune system work better

Support Therapy

Weakness of muscles can cause a loss of function. Therapy may help you work around these changes. Options include:

  • Physical therapy—stretching and strengthening to regain function as soon as possible
  • Occupational therapy and Dietitian—if chewing and swallowing has become difficult
  • Speech therapy—to address speech problems caused by weak neck muscles


There are no ways to prevent polymyositis.


American Autoimmune Related Diseases Association  http://www.aarda.org 

The Myositis Association  http://www.myositis.org 


The Arthritis Society  http://www.arthritis.ca 

Health Canada  https://www.canada.ca 


Diagnosis. The Myositis Association website. Available at: http://www.myositis.org/learn-about-myositis/diagnosis. Updated March 2015. Accessed May 11, 2016.

Gordon PA, Winer JB, Hoogendijk JE, Choy EH. Immunosuppressant and immunomodulatory treatment for dermatomyositis and polymyositis. Cochrane Database Syst Rev. 2012;8:CD003643.

Idiopathic inflammatory myopathy. EBSCO DynaMed Plus website. Available at:  https://www.dynamed.com/topics/dmp~AN~T115684/Idiopathic-inflammatory-myopathy  . Updated November 20, 2017. Accessed June 13, 2018.

Myositis. Ortho Info—American Academy of Orthopaedic Surgeons website. Available at: http://orthoinfo.aaos.org/topic.cfm?topic=A00198. Updated June 2017. Accessed June 13, 2018.

NINDS polymyositis information page. National Institute of Neurological Disorders and Stroke website. Available at: https://www.ninds.nih.gov/Disorders/All-Disorders/Polymyositis-Information-Page. Accessed June 13, 2018.

Treatment and disease management. Myositis Association website. Available at: http://www.myositis.org/learn-about-myositis/treatment. Accessed June 13, 2018.

Types of myositis. Myositis Association website. Available at: http://www.myositis.org/learn-about-myositis/types-of-myositis. Accessed June 13, 2018.

11/9/2015 DynaMed Plus Systematic Literature Surveillance  https://www.dynamed.com/topics/dmp~AN~T115684/Idiopathic-inflammatory-myopathy  : Kuo CF, Grainge MJ, Valdes AM, et al. Familial aggregation of systemic lupus erythematosus and coaggregation of autoimmune diseases in affected families. JAMA Intern Med. 2015;175(9):1518-1526.

Revision Information

  • Reviewer: EBSCO Medical Review Board Rimas Lukas, MD
  • Review Date: 05/2018
  • Update Date: 06/12/2018