What is dermatomyositis?

Dermatomyositis is a chronic inflammatory disease involving the skin and skeletal muscles. Its etiology is unknown. Polymyositis is the term used for involvement of the skeletal muscles without cutaneous involvement. The muscle involvement usually presents as proximal muscle weakness, sometimes with pain, and later with muscle atrophy. Muscle involvement may precede, follow, or occur simultaneously with skin disease and, in some instances, may not be detectable, a condition called amyopathic dermatomyositis. A number of cutaneous changes are present, including blotchy erythema, erythematous to violaceous papules and plaques particularly on extensor surfaces, poikilodermatous changes, and calcinosis cutis.

Euwer RL, Sontheimer RD: Amyopathic dermatomyositis (dermatomyositis siné myositis): presentation of six new cases and review of the literature, J Am Acad Dermatol 24:959–966, 1991.