What is myositis?
Myositis means muscle inflammation, and can be caused by infection, injury, certain medicines, exercise, and chronic disease. Some of the chronic, or persistent, forms are idiopathic inflammatory myopathies, and those are the diseases we discuss here. "Idiopathic" means that the cause is unknown.
An introduction to myositis by TMA Medical Advisor Dr. Chet Oddis
What are inflammatory myopathies?
Myositis is the popular term used to describe a number of inflammatory myopathies:
- dermatomyositis (DM)
- inclusion-body myositis (IBM)
- juvenile forms of myositis (JM)
- polymyositis (PM)
These diseases cause swelling and loss of muscle. They are also called idiopathic inflammatory myopathies. "Idiopathic" means the causes are unknown.
Inflammatory myopathies are thought to be autoimmune diseases, meaning the body's immune system, which normally fights infections and viruses, is misdirected and attacks the body's own normal, healthy tissue through inflammation, or swelling. All of these diseases can cause muscle weakness, but each type is different. Learn more about autoimmunity.
Signs and symptoms:
- Muscle weakness, sometimes with muscle pain
- General tiredness and fatigue
- Trouble climbing stairs, standing from a seated position, or reaching up
- Difficulty swallowing
For more specific signs and symptoms, click the different disease types listed above.
Updated February 2014