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 affected as well. There are forms of myositis that are linked to inflammation in the lung.

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, the immune system attacks the body's own tissues. Health experts don't know why this happens. Skin, muscle tissue, or both are often involved. Other parts of the body may also be affected. This includes the lungs. 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 it hard to climb stairs, get out of chairs, lift heavy things, or raise arms overhead. The muscles in the throat can also be affected. This can lead to trouble swallowing. People with dermatomyositis often have skin changes. This may include 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. But in many cases the disease is long-lasting (chronic). There are times when symptoms are worse (active disease). These may be followed by times when symptoms get better or go away (remission).

Treatment may include steroid medicines taken by mouth (oral). It may also include medicines that suppress the immune system. Rest, physical therapy, and exercise may help ease symptoms.

Home care

  • Take any prescribed medicines as advised.

  • Stay active. Exercise and physical activity help to keep your muscles in top shape. Talk with your provider about an activity plan that's right for you.

  • If your muscles ache, rest as needed.

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

  • If you have trouble swallowing, talk with your provider. They can make 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 provider visits. Get all your advised screening testing.

  • If you're disabled because of severe disease, talk to your employer. Work with them to make reasonable accommodations when needed.

Follow-up care

Follow up with your healthcare provider as advised. Find more information at:

When to get 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 look of a wart or mole

  • Lasting cough, hoarseness, or coughing up blood

  • Night sweats or unexplained fevers

  • Shortness of breath

  • Muscle pain gets worse

  • Joint swelling

  • Symptoms get worse

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