Stem Cell Transplantation After Reduced-Dose Chemotherapy for Patients With Sickle Cell Disease or Thalassemia

Inclusion criteria: * All patients must: * Have related donors who are identical at 6 human leukocyte antigens (HLA) loci (A, B and DR) by molecular typing * Have a performance status from 0-2 * Give written informed consent * Patients with sickle cell disease should have 1 or more of the following: * Acute chest syndrome requiring recurrent hospitalization or exchange transfusion * Nonhemorrhagic stroke or central nervous system event lasting longer than 24 hours * Recurrent vaso-occlusive pain (2 episodes or more per year) or recurrent priapism * Sickle nephropathy (moderate or severe proteinuria or a glomerular filtration rate 30-50 percent of normal predicted value) * Bilateral proliferative retinopathy and major visual impairment in at least 1 eye * Osteonecrosis of multiple joints * Patients with thalassemia should have 1 or more of the following: * Transfusion dependence, defined as a transfusion requirement of greater than or equal to 6 units of packed red blood cells over the past 12 months * Iron overload, defined as serum ferritin greater than 500 mcg/L in the absence of infection or biopsy-proven iron overload * Presence of 2 or more alloantibodies against red cell antigens Exclusion criteria: * Pregnancy * Acute hepatitis (transaminases greater than 3 times the normal value) * Cardiac ejection fraction less than 30 percent * Severe renal impairment (glomerular filtration rate less than 30 percent of predicted normal value) * Severe residual functional neurologic impairment (other than hemiplegia alone) * Seropositivity for the human immunodeficiency virus (HIV)