Polymyositis (PM) does not have the characteristic rash of Dermatomyositis (DM).  Onset of muscle weakness usually progresses slower than DM.  Proximal (nearest to the trunk of the body) limb and neck muscles are weakened, involvement of distal (farthest from the trunk of the body) muscles varies.  Difficulty swallowing is common in PM.  Inability to breathe due to muscle failure is uncommon, but occurs more often in PM than in DM or IBM.  As many as one third of PM patients have muscle pain, but it is rarely a chief complaint.

Polymyositis literally translated means "inflammation of many muscles."  PM is a disease characterized by generalized weakness - often without pain.  The peak onset is between the ages of 30 and 60+.   PM rarely affects people under the age of 20, but cases of childhood and infant PM have been reported.  More women than men are affected with PM.

High doses of Prednisone has been an effective treatment for many patients.  Other immunosuppressants such as Azathioprine and Methotrexate are also used.  Unfortunately, these drugs have side effects, especially with prolonged use.  Patients who do not respond well to Prednisone or other drugs may be treated with IVIg.