Polymyositis is a 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. The muscles become inflamed or swollen. This causes pain. The disease is progressive and starts slowly. If untreated, the muscles gradually become weaker. The pain in the muscles also increases.
This rare disease is believed to be an autoimmune disorder. Your immune system is your body’s defense system. It fights diseases and infections. In this case your immune system attacks your own muscle tissue by mistake.
The sooner the disease is treated, the better the outcome. If you suspect you have this condition, contact your doctor.
The cause is unknown. Factors that may contribute to polymyositis include:
The following factors increase your chance of developing polymyositis:
This diagnosis is not easy. Symptoms vary from person to person. It is often a matter of ruling out other diseases and conditions. Your doctor will ask about your symptoms and medical history. A physical exam will be done.
Tests may include the following:
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:
There are a number of medicines that may be prescribed. Corticosteroids (eg, prednisone) are usually one of the first treatments that are tried. These medicines work by suppressing the immune system, which reduces inflammation. In some cases, it may take 3-6 months to have an improvement in symptoms.
Other medicines that may be recommended instead of prednisone include:
Intravenous immunoglobulin is another treatment option that 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.
In severe cases of polymyositis, the doctor may recommend investigational drugs, such as:
Your doctor may recommend that you work with a physical therapist to prevent permanent muscle damage. Exercise may include:
Polymyositis can lead to problems with chewing and swallowing. By working with a registered dietician, you can learn ways to adjust to these changes and get the nutrition that you need.
Polymyositis may also cause speech problems. A speech therapist can assess your condition and create a program for you.
American Autoimmune Related Diseases Association
The Myositis Association
The Arthritis Society
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Myositis Association. Myositis FAQ. Myositis Association website. Available at: http://www.myositis.org/learn-about-myositis/types-of-myositis. Accessed September 12, 2005.
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Last reviewed [Under Medical Review] by Rosalyn Carson-DeWitt, MD
Last Updated: 12/30/2011