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Dermatomyositis is a muscle disease that involves inflammation and a skin rash. It is a type of inflammatory myopathy.
The cause of dermatomyositis is unknown. Experts think it may be due to a viral infection of the muscles or a problem with the body's immune system. It may also occur in patients who have cancer in the abdomen, lung, or other parts of the body.
Anyone can develop dermatomyositis. It most commonly occurs in children age 5 - 15 and adults age 40 - 60. Women develop this condition more often than men.
Polymyositis is a similar condition, but the symptoms do not include a skin rash.
The muscle weakness may come on suddenly or develop slowly over weeks or months. You may have trouble raising your arms over your head, getting up from a sitting position, and climbing stairs.
The rash may appear on your face, knuckles, neck, shoulders, upper chest, and back.
The doctor will do a physical exam. Tests may include:
The disease is treated with anti-inflammatory medicines called corticosteroids and other drugs that suppress the immune system.
When your muscles get stronger, your doctor may tell you to slowly cut back on your doses. Most people with this condition must take a medicine called prednisone for the rest of their lives.
If a tumor is causing the condition, the muscle weakness and rash may get better when the tumor is removed.
Symptoms may go away completely in some people, such as children.
The condition may be fatal in adults due to severe muscle weakness, malnutrition, pneumonia, or lung failure. The major causes of death with this condition are cancer and lung disease.
Call your health care provider if you have muscle weakness or other symptoms of this condition.
Jorizzo JL, Vleugels RA. In: Bolognia JL, Jorizzo JL, Schaffer JV, et al, eds. Dermatology. 3rd ed. Philadelphia, Pa: Mosby Elsevir; 2012:chap 42.