For patients with advanced or rapidly progressive disease, the morbidity and mortality with transplantation is unacceptably high. Unfortunately, there are no viable alternative therapeutic options for these patients; if transplantation is not performed the patients are sent home to die. Our group at Minnesota has developed a new protocol incorporating transplantation using a reduced intensity conditioning regimen designed to decrease toxicity associated with the transplant procedure. This regimen will make use of the drug clofarabine, which has lympholytic and immune suppressive properties without the neurologic toxicity observed in the related compound, fludarabine, commonly used for transplantation. In addition, several agents providing anti-oxidant and anti-inflammatory properties will be used to assist in the stabilization of the disease processes. This revised transplant protocol will test the following: 1) the ability to achieve engraftment with the reduced intensity protocol, 2) the mortality associated with transplant by day 100, 3) patient outcomes, based on differential neurologic, neuropsychologic, imaging and biologic evaluations prior to transplantation and at designated points after transplantation (day 100, 6 months, 1, 2 and 5 years). Additional biologic studies will include pharmacokinetics of clofarabine and mycophenolate mofetil (MMF). In addition, for patients undergoing lumbar puncture studies, cerebrospinal fluid (CSF) will be requested for determinations of biologic parameters.