Most patients with autoimmune diseases are thought to have a a normal life expectancy, and thus are treated conservatively. However, these diseases have a diverse clinical course. A small subset of patients have "severe autoimmune diseases," or SADS, which are rapidly progressive and are associated with early mortality. If patients with SADS can be identified before they develop irreversible organ damage, aggressive intervention would be indicated. Consequently, patients with SADS are now being enrolled in experimental protocols of immune ablation and hematopoietic stem-cell rescue (ie, bone marrow transplantation [BMT] at several US institutions. For various reasons, including the high cost of BMT, it will probably be years before the benefits, if any, of this procedure are known.