 The main purpose of this study is to determine the safety and effectiveness of high-dose immunosuppressive therapy followed by reinfusion transplantation of the participants own autologous self peripheral blood stem cells PBSCs compared to treatment with monthly for 12 months intravenous doses of cyclophosphamide Cytoxan therapy for the treatment of severe systemic sclerosis SSc. These treatments are being given in order to determine if they will slow down or stop SSc from becoming more severe, and if they can reverse the effects of the disease. The researchers are evaluating the effects of the two treatments on serious organ damage and survival related to SSc, while also looking at the side effects of the two treatments. 