Myositis (my-uh-SY-tis) is inflammation of the muscles that can be caused by many conditions and diseases that make muscles weak, swollen, and irritated.
In all types of myositis, something causes the immune system to attack healthy muscle tissue. This can be due to infection, trauma, a drug reaction, or an autoimmune-related disease, and can cause muscle weakness, swelling, and pain. In rare cases, myositis that affects neck or chest muscles can make it hard to swallow or breathe.
Myositis can range from mild to severe. Some cases cause only mild weakness and may go away on their own, especially if due to a viral infection. Other cases can make routine movements difficult and may cause long-term medical problems if left untreated.
There is no cure for myositis, but in most cases, treatment with rest, good fluid intake, and sometimes medications can limit the damage to muscle tissue and help increase strength. If myositis is due to an autoimmune disease, proper treatment can keep the disease under control.
All A to Z dictionary entries are regularly reviewed by KidsHealth medical experts.
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