Myositis is an inflammation or swelling of the muscles, usually caused by injury, infection, medications, or an autoimmune disorder.
Miller FW. Polymyositis and dermatomyositis. In: Goldman L, Schafer AI, eds.Cecil Medicine
Update Date 4/18/2013
Updated by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.