Dermatomyositis (DM) is a condition that can cause muscle weakness and skin rashes. Both the skin and the muscles become inflamed in DM. Furthermore, a minority of individuals with DM will also develop lung problems. It is not certain as to what the cause of DM is, but it is believed that it is caused by an immune-mediated process triggered by outside factors (e.g. drugs, infectious agents) in genetically predisposed individuals. Adult women are affected twice as often as men yet in children it does not affect one sex over another. The incidence of DM is 2-7 per million individuals. The peak incidence of BM occurs in children 10-15 years and adults 45-47 years.