Alemtuzumab, Fludarabine, and Busulfan Followed By Donor Stem Cell Transplant in Treating Young Patients With Hematologic Disorders

DISEASE CHARACTERISTICS:

Diagnosis of 1 of the following hematologic conditions:

Aplastic anemia with marrow aplasia, meeting all of the following criteria:

Absolute neutrophil count < 500/mm^3
Platelet and/or red cell transfusion dependent

Chronic aplastic anemia, meeting all of the following criteria:

Transfusion dependent
Unresponsive to immunosuppressive therapy
Alternative matched unrelated donor has been identified

Congenital marrow failure syndrome, including any of the following (with closely matched related or unrelated donor):

Primary red cell aplasia (Diamond-Blackfan syndrome)
Congenital neutropenia (Kostmann's syndrome)
Amegakaryocytic thrombocytopenia
Congenital dyserythropoietic anemias
Other severe acquired cytopenias in which a transplantation using a combined busulfan/cyclophosphamide conditioning regimen is indicated

Hemoglobinopathy (with closely matched related or unrelated donor)

β-thalassemia major
Sickle cell anemia
Hemoglobin E/β-thalassemia

Severe immunodeficiency disease

Chediak-Higashi disease
Wiskott-Aldrich syndrome
Combined immunodeficiency disease (Nezelof's)
Hyper immunoglobulin M (IgM) syndrome
Bare lymphocyte syndrome
Chronic granulomatous disease
Familial erythrohemophagocytic lymphohistiocytosis
Other stem cell defects (e.g., osteopetrosis)

Severe immune dysregulation/autoimmune disorders

Achieved a transient response to prior immunosuppressive therapy

Chronic myelogenous leukemia

Disease in first chronic phase

Acute myeloid leukemia

Disease in first remission
Myelodysplastic syndromes
Inborn errors of metabolism
Histiocytosis
No severe combined immunodeficiency disease

Matched related or unrelated donor available by high resolution DNA typing

Related donor, meeting both of the following criteria:

Matched at both human leukocyte antigen (HLA)-Drβ1 alleles
No more than 1 mismatch at the 4 HLA-A and -B alleles

Unrelated donor, meeting 1 of the following criteria:

Marrow matched at both HLA-Drβ1 alleles AND no more than 1 mismatch at the 4 HLA-A and -B alleles
Umbilical cord blood matched at 5/6 HLA-A, -B, and -DRβ1 alleles with at least 1 -DRβ1 match AND there are ≥ 3x10^5 CD34+ (Cluster of differentiation 34-positive) cells per kg body weight of recipient available at the time of cryopreservation

PATIENT CHARACTERISTICS:

Cardiac ejection fraction ≥ 27%
Creatinine clearance ≥ 50 mL/min by 24-hour urine collection or glomerular filtration rate
DLCO (diffusion capacity of lung for carbon monoxide) ≥ 50% of predicted (corrected for anemia/lung volume)

PRIOR CONCURRENT THERAPY:

No prior transplantation for leukemia from which patient remains engrafted and alemtuzumab is not needed as part of the conditioning regimen