Myositis is a disease, believed to be due to immune cells, cells which normally protect the body, but are now attacking the muscles and other organ systems within body. As a result, the affected muscles and organs fail to work properly causing weakness, difficulty swallowing, skin rash, respiratory problems, heart problems, joint stiffness, soft tissue calcification and vasculitis (blood circulation problems). The likelihood of progression of this disease is high. This study is designed to examine whether treating patients with high dose cyclophosphamide (a drug which reduces the function of the immune system) and ATG (a protein that kills the immune cells that are thought to be causing this disease), followed by return of previously collected blood stem cells will stop the progression of myositis.