Busulfan, Antithymocyte Globulin, and Fludarabine Followed By a Donor Stem Cell Transplant in Treating Young Patients With Blood Disorders, Bone Marrow Disorders, Chronic Myelogenous Leukemia in First Chronic Phase, or Acute Myeloid Leukemia in First Remission

DISEASE CHARACTERISTICS:

• Diagnosis of one of the following hematopoietic disorders:

  • Severe aplastic anemia with marrow aplasia (i.e., absolute neutrophil count \< 500/mm\^3, platelet and/or red blood cell transfusion dependent), meeting 1 of the following criteria:

    • Closely matched related donor
    • Unresponsive to immunosuppressive therapy within 3 months after follow-up AND alternative matched unrelated donor available

  • Congenital marrow failure syndrome, including any of the following:

    • Primary red blood cell aplasia (Diamond-Blackfan syndrome)
    • Congenital neutropenia (Kostmann's syndrome)
    • Amegakaryocytic thrombocytopenia

  • Hemoglobinopathy including any of the following:

    • β-thalassemia major
    • Sickle cell anemia

  • Severe immunodeficiency disease including any of the following:

    • Chediak-Higashi disease
    • Wiskott-Aldrich syndrome
    • Combined immunodeficiency disease (Nezelof's)
    • Hyperimmunoglobulin M syndrome
    • Bare lymphocyte syndrome
  • Other stem cell defects (e.g., osteopetrosis)

  • Chronic myelogenous leukemia in first chronic phase

    • Not eligible for other ongoing phase II/III studies

  • Acute myeloid leukemia in first remission

    • Not eligible for other ongoing phase II/III studies
  • Inborn errors of metabolism
• No severe combined immunodeficiency disorder

• Available donor, meeting 1 of the following criteria:

  • Related donor matched by high resolution DNA typing at both HLA Drβ1 alleles and ≤ 1 mismatch at the 4 HLA-A and -B alleles

  • Unrelated donor, meeting one of the following criteria:

    • Bone marrow matched by high resolution DNA typing at both HLA Drβ1 alleles and ≤ 1 mismatch by high resolution DNA typing at the 4 HLA-A and -B alleles
    • Umbilical cord blood matched at 4/6 HLA-A, -B, and Drβ1 alleles by high resolution typing with ≥ 1 Drβ1 match and ≥ 3 X 10\^7 cells/kg body weight of recipient

PATIENT CHARACTERISTICS:

• See Disease Characteristics
• No active bacterial, viral, or fungal infection
• Cardiac shortening fraction ≥ 27%
• Creatinine clearance ≥ 60 mL/min
• DLCO ≥ 60% of predicted (corrected for anemia/lung volume)

PRIOR CONCURRENT THERAPY:

• See Disease Characteristics