Polymyositis and Dermatomyositis

What are polymyositis and dermatomyositis?

Polymyositis (PM) is a chronic disease that causes inflammation and weakness of the muscles. Dermatomyositis (DM) is a related disease in which a skin rash occurs along with the muscle problems of polymyositis. In about half of the people who have PM or DM, the heart muscle is affected. Both of these diseases are rare.

How do they occur?

PM or DM probably occurs when the body's immune system attacks its own tissues. It is not known why this happens. Sometimes cancer may help cause the disease. PM or DM occurs most often in adults age 50 to 70, or in children 5 to 15 years old.

What are the symptoms?

Polymyositis can begin suddenly or slowly. Symptoms may include:

• weakness, especially in the hips, thighs, upper arms, and shoulders
• muscle and joint pain
• weight loss
• tiredness
• fever
• tremors of the hands
• shortness of breath, even at rest
• problems swallowing.

If you have dermatomyositis, you also have a violet or deep reddish-purple rash.

How are they diagnosed?

Your healthcare provider will ask about your medical history and your symptoms and examine you. The inflammation causes a breakdown of muscle cells, so you may have a blood test to look for abnormal amounts of broken cells. Other types of tests might include:

• Biopsy of the affected area (the removal of a small sample of muscle after you are given an anesthetic) to check for inflammation.
• An electromyogram (EMG), which is a test that looks at muscle strength and function.
• Blood tests to check for substances called autoantibodies. These substances are made by your immune system and can attack your own tissues.

How are they treated?

There is no known cure for PM or DM. Treatments might include:

• Physical therapy to prevent more weakness.
• Treatment for other symptoms such as shortness of breath or pain.
• Prednisone or other anti-inflammatory drugs. These drugs work better for some people than for others. If further treatment is needed, powerful drugs that interfere with the body's normal immune system may be used. These more powerful drugs are the same drugs used to control the rejection problem in heart and kidney transplants and must be used very carefully.

You may need to see a rheumatologist, a specialist in diseases of connective tissue.

How long will effects last?

It is difficult to predict the course of this disease. Once diagnosed you might:

• have a severe episode at the time of diagnosis and then do well
• have ongoing flare-ups of the disease, but not much worsening of your symptoms
• have it affect your breathing muscles or heart.

If you have complications affecting your breathing or heart, you will need to work very closely with your healthcare provider to manage your disease.

How can I help take care of myself?

• Carefully follow your healthcare provider's instructions for any medicines you are taking or other treatments.
• Regular exercise and physical therapy can help prevent loss of skin and muscle flexibility that can occur with this disease.
• Do what you can to keep your bones healthy. Steroid medicines, such as prednisone, are often used for this disease and can weaken bones. Check with your healthcare provider about taking calcium and vitamin D supplements. You may need additional medicines, such as alendronate, to help prevent loss of bone (osteoporosis).
• Dermatomyositis and polymyositis can increase the risk of several types of cancer. Be sure you stay up to date on all recommended cancer screening tests, such as mammograms for breast cancer screening and colonoscopy for colon cancer screening.
• Avoid getting too much exposure to sunlight.
• Watch for signs of infection. Medicines like prednisone can suppress the immune system and make you more prone to infection. Call your healthcare provider if you have high fever, shaking chills, or other symptoms of infection.
• Call your provider right away if you have shortness of breath and trouble swallowing.