Dermatomyositis (DM) is an autoimmune inflammatory condition affecting the skin and skeletal muscle. Characteristic skin findings along with symmetric proximal extensor muscle weakness help define this condition. DM is seen in both children and adults, affecting approximately 10 cases per million in US adults and 3.2 cases per million in US children. The exact mechanism of DM is unknown however previous studies suggest autoimmune, genetic, and environmental causes. This book reviews the diagnosis, risk factors and available treatment options for dermatomyositis.