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Polymyositis (PM)
Definition - one of a group of muscle diseases
that involve inflammation of the muscles or associated tissues; the
inflammatory cells of the immune system directly attack muscle fibers
Cause - the cause is unclear; researchers suspect viruses or exposure to
certain drugs might trigger the misdirected immune response
Onset - usually begins after age 20; more common in females than in males
Symptoms - weakness of the muscles of the hips, thighs, upper arms, top
part of the back, shoulders and muscles that move the neck; pain or tenderness
in affected areas; possible heart, respiratory and swallowing problems
Progression - gradual; immunosuppressant medications often effectively
control symptoms
Inheritance - not a genetic disease, though a genetic predisposition may
exist
