What is polymyositis?

Polymyositis is a disease that causes chronic muscle inflammation and weakness. If left untreated, it can ultimately inhibit the patient's ability to walk.

Fortunately, treatment is often successful in reversing the symptoms. The disease affects the skeletal muscles - those involved with movement - and is a systemic illness because it may affect the whole body. The onset of polymyositis is often sudden but then the disease usually progresses slowly. Polymyositis patients will experience flare-ups (periods of increased symptoms) and remissions, when there are minimal or no symptoms. 

Polymyositis occurs in all age groups, although it is most common in children between 5 and 15 and in adults between the ages of 50 and 70, with women affected more often than men. The disease occurs more frequently among African Americans than Caucasians.1

Sometimes polymyositis or the related illness dermatomyositis are associated with cancer or other connective tissues diseases such as scleroderma, rheumatoid arthritis, lupus or with infectious disorders such as HIV-AIDS. 

What causes polymyositis?

While there is no known cause of polymyositis, it is an autoimmune disease that occurs when the body's immune system attacks muscle cells, resulting in muscle breakdown. Evidence suggests that genetics play a part in causing polymyositis. 

What are the symptoms of polymyositis?

Polymyositis is a systemic disease, which means it affects the whole body.  As the disease progresses and muscle power is lost, patients may experience a range of symptoms, including:

  • Muscle weakness, usually in those that are closest to the body's trunk
  • Loss of strength, difficulty climbing stairs, getting up from a chair, or lifting above the shoulder
  • Joint pain or muscle tenderness
  • Difficulty swallowing
  • Shortness of breath
  • Fatigue
  • General malaise
  • Weight loss
  • Low grade fever

How is polymyositis treated?

Early treatment of polymyositis and its flares is especially important and can often be successful in reversing symptoms. Treatment is aimed at decreasing the inflammation in the muscles and monitoring for signs of other diseases. At first, your doctor will prescribe high doses or corticosteroids. Often, the disease goes into remission but long-term rehabilitation of weakened muscles may be needed.
Learn more about treatment for polymositis at Temple.

To schedule an appointment with a Temple Rheumatologist, click here or call 1-800-TEMPLE-MED (1-800-836-7536).

U.S. National Library of Medicine