Definition - one of a group of muscle diseases that involve inflammation of the muscles or associated tissues; the inflammatory cells of the immune system attack the blood vessels that supply muscles and skin

Cause - the cause is unclear; researchers suspect viruses or exposure to certain drugs might trigger the misdirected immune response

Onset - childhood to adulthood

Symptoms - distinctive reddish or purplish rash; rough, scaly skin; hard, painful calcium nodules under the skin; weakness of the muscles of the hips, thighs, upper arms, top part of the back, shoulders and muscles that move the neck; possible heart, respiratory and swallowing problems; possible joint pain

Progression - gradual; immunosuppressant medications often effectively control symptoms

Inheritance - not a genetic disease, though a genetic predisposition may exist

Facts About Inflammatory Myopathies