Myositis means muscle inflammation. There are various forms of myositis. One form is polymyositis, which affects muscles throughout the body. Another is dermatomyositis, which affects both muscle and skin. Other body tissues can be involved as well.

Myositis is thought to be an immune system problem. Immune cells in the body are designed to attack and destroy invading viruses and harmful bacteria. In myositis, for unknown reasons, the immune system attacks the body's own tissues. Skin, muscle tissue, or both are often involved. Other parts of the body, such as the lungs, may also be affected. Myositis may be triggered by exposure to certain chemicals, medicines, or viruses. But often a cause can't be found. This is known as idiopathic myositis.

The main symptom of myositis is muscle weakness or aching (especially large muscles such as those on the thighs, hips, shoulders, neck, and trunk). This can make climbing stairs, getting out of chairs, lifting heavy things, or raising arms overhead difficult. The muscles in the throat can also be involved. This can lead to trouble swallowing. People with dermatomyositis often develop skin changes, including a rash. Children may have different symptoms from adults.

People with myositis should be assessed for lung disease.

Some people have only mild symptoms that get better with treatment. In many cases, though, the disease is chronic (long-lasting). Periods when symptoms are worse (active disease) may be followed by periods where symptoms get better or go away (remission). 

Treatment of myositis may include oral steroid medicines and medicines that suppress the immune system. Rest, physical therapy, and exercise may help ease symptoms.

Home care

  • Take any prescribed medicines as directed.

  • Remain physically active. Exercise and physical activity help to keep your muscles in the best shape possible. Talk with your healthcare provider about an activity plan that is right for you.

  • If you are having muscle aches, rest as needed.

  • If directed, stay out of the sun. The sun can make a skin rash worse.

  • If you have trouble swallowing, talk with your healthcare provider about making changes to your diet. This can help prevent breathing food into your lungs. This can lead to pneumonia and other problems.

  • Stay up to date on all healthcare provider appointments and recommended screening testing.

  • If you are disabled because of severe disease, work with your employer to arrange for reasonable accommodations when needed.

Follow-up care

Follow up with your healthcare provider, or as advised. These organizations can give more information:

  • Myositis Association,

  • Arthritis Foundation,, 800-283-7800

When to seek medical advice

Call your healthcare provider right away if any of these occur: 

  • Change in bowel or bladder habits

  • Blood in the stool (black or red color)

  • Unexpected weight loss

  • A lump in the breast or elsewhere

  • Breathing in food when eating (aspiration)

  • Change in the appearance of a wart or mole

  • Persistent cough, hoarseness, or coughing up blood

  • Night sweats or unexplained fevers

  • Shortness of breath

  • Worsening muscle pain

  • Swelling of joints

  • Worsening symptoms

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