CD34+ stem cell selection in children, adolescents and young adults receiving partially matched family donor or matched unrelated adult donor allogeneic bone marrow or peripheral blood stem cell transplant will be safe and well tolerated and be associated with a low incidence of serious (Grade III/IV) acute and chronic graft versus host disease (GVHD).

The selection of CD34+ cells is associated with the simultaneous depletion of T cells that are responsible for severe acute and chronic graft versus host disease (GVHD). Successful engraftment is reported in adult patients with malignant and non-malignant disease who received CD34+ selected stem cells from HLA-matched or mismatched mobilized peripheral blood (PBSC) or bone marrow.

Study Design:

Selected patients defined in the eligibility criteria will enrolled on this study. Patients will receive one of either full intensity or reduced intensity regimen based on the patient's disease status, organ function and performance and determined by the PI and will have peripheral blood undergo CD34 selection.

Inclusion Criteria:

• Adequate renal function defined as:Serum creatinine <1.5 x normal, or Creatinine clearance or radioisotope GFR >60 ml/min/m2 or an equivalent GFR as determined by the institutional normal range.
• Adequate liver function defined as:Total bilirubin <1.5 x normal, or SGOT (AST) or SGPT (ALT) <3.0 x normal
• Adequate cardiac function defined as:Shortening fraction >27% by echocardiogram, or Ejection fraction of >47% by radionucleotide angiogram or echocardiogram.
• Adequate pulmonary function defined as:Uncorrected DLCO >50% by pulmonary function test. For children who are uncooperative, no evidence of dyspnea at rest, no exercise intolerance, and a pulse oximetry >94% on room air.

Eligibility for Reduced Intensity Regimen:

• Adequate renal function defined as:Serum creatinine 2.0 x normal, or creatinine clearance or radioisotope GFR > 40 ml/min/m2 or an equivalent GFR as determined by the institutional normal range.
• Adequate liver function defined as:Total bilirubin < 2.5 x normal; or SGOT (AST) or SGPT (ALT) < 5.0 x normal.
• Adequate cardiac function defined as:Shortening fraction of >25% by echocardiogram, or Ejection fraction of >40% by radionuclide angiogram or echocardiogram.
• Adequate pulmonary function defined as:DLCO >35% by pulmonary function test. For children who are uncooperative, no evidence of dyspnea at rest, no exercise intolerance, and a pulse oximetry >94% in room air.

Exclusion Criteria:

• Pregnancy/Breast Feeding: Females who are pregnant or breast-feeding are not eligible.
• Infection: Patients with documented uncontrolled infection at the time of study entry are not eligible.