Juvenile dermatomyositis (JDM) is a rare, childhood autoimmune disease that primarily affects muscle and skin, causing weakness and rashes. Many children with JDM do not respond fully to our initial therapies of steroids, methotrexate, and immune globulin, and for these patients, we do not always know the next best medicines. Likewise, we know that JDM occurs because of imbalances in our immune system. However, we do not know the specific parts of the immune system that are affected. In this study, we will apply two technologies that measure the genes expressed and the proteins present in JDM patients who have a good response to therapy after 6 months of treatment and those who do not. By measuring the genes and proteins together, we will have a better understanding of how the immune system is working in JDM and how we can better target these imbalances with new medicines.