Polymyositis is a rare disease of the muscles. It usually affects the muscles closest to the trunk of the body. However, it may affect muscles anywhere in the body.
Front Muscles of Trunk
Polymyositis may be caused by a combination of genetic and environmental factors that trigger an abnormal immune response.
Polymyositis is more common in women and in people aged 31-60 years old.
Polymyositis causes muscles become inflamed or swollen. Symptoms may include:
- Muscle weakness
- Muscle pain that increases over time
- Great effort needed to climb stairs
- Trouble rising from a chair
- Difficulty reaching overhead
- Chronic dry cough
You will be asked about your symptoms and medical history. A physical exam will be done.
Your bodily fluids and tissues may be tested. This can be done with:
- Blood tests
- Muscle biopsy
Your muscle activity may be measured. This can be done with an electromyogram (EMG).
Images may be taken of your bodily structures. This can be done with an MRI scan.
The disease is progressive and starts slowly. If untreated, the muscles gradually become weaker. The pain in the muscles also increases. While there is no cure, treatment can improve your muscle strength and function. Talk with your doctor about the best plan for you. Options include:
Medications to treat polymyositis may include:
- Corticosteroids to reduce inflammation
- Topical steroids to treat skin rash
IV immunoglobulin therapy is another treatment option. It involves using an IV needle to inject extra immunoglobins (special proteins) into the body. This process may help the immune system function better and reduce inflammation.
Your doctor may recommend that you work with a physical therapist to prevent permanent muscle damage. Exercise may include:
- A regular stretching routine for weakened arms and legs
- Light strengthening as the pain lessens and function returns
Polymyositis can lead to problems with chewing and swallowing. By working with a registered dietitian, you can learn ways to adjust to these changes and get the nutrition that you need.
There are no current guidelines to prevent polymyositis.
American Autoimmune Related Diseases Association
The Myositis Association
The Arthritis Society
Choy EH, Hoogendijk JE, Lecky B, Winer JB, Gordon P. Immunosuppressant and immunomodulatory treatment for dermatomyositis and polymyositis. Cochrane Database Syst Rev. 2009;(4):CD003643.
Diagnosis. The Myositis Association website. Available at: http://www.myositis.org/learn-about-myositis/diagnosis. Updated March 2015. Accessed June 26, 2015.
Idiopathic inflammatory myopathy. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated May 4, 2015. Accessed June 23, 2015.
Myositis. American Academy of Orthopaedic Surgeons Ortho Info website. Available at: http://orthoinfo.aaos.org/topic.cfm?topic=A00198. Updated July 2007. Accessed June 23, 2015.
Treatment. Myositis Association website. Available at: http://www.myositis.org/learn-about-myositis/treatment. Updated March 2015. Accessed June 23, 2015.
Types of myositis. Myositis Association website. Available at: http://www.myositis.org/learn-about-myositis/types-of-myositis. Updated January 2015. Accessed June 23, 2015.
NINDS Polymyositis information page. National Institute of Neurological Disorders and Stroke website. Available at: http://www.ninds.nih.gov/disorders/polymyositis/polymyositis.htm. Updated February 23, 2015. Accessed June 23, 2015.
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Last reviewed June 2015 by John C. Keel, MD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.