Definition

Polymyositis is a disease of the muscles. It usually affects the muscles closest to the trunk of the body. However, it may affect muscles anywhere in the body. The muscles become inflamed or swollen. This causes pain. The disease is progressive and starts slowly. If untreated, the muscles gradually become weaker. The pain in the muscles also increases.

Front Muscles of Trunk

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This rare disease is believed to be an autoimmune disorder. Your immune system is your body’s defense system. It fights diseases and infections. In this case your immune system attacks your own muscle tissue by mistake.

The sooner the disease is treated, the better the outcome. If you suspect you have this condition, contact your doctor.