Inclusion Criteria

DISEASE CHARACTERISTICS:

- Diagnosis of 1 of the following hematologic malignancies:

- Acute myeloid leukemia (AML)*

- With or without history of myelodysplastic syndromes (MDS)

- Patients in first complete remission (CR) (no greater than 5% blasts in
marrow) with translocations t(8;21) and inv(16) are allowed provided they
failed first-line induction therapy

- Patients in first CR (no greater than 5% blasts in marrow) with
translocations t(15;17) are allowed provided at least 1 of the following is
true:

- Failed first-line induction therapy

- Molecular evidence of persistent disease

- No patients in first CR and with Down syndrome

- Acute lymphoblastic leukemia (ALL)*, meeting 1 of the following criteria:

- Not in first CR (no greater than 5% blasts in marrow)

- In first CR and high risk as defined by 1 of the following:

- Hypoploidy (no more than 44 chromosomes)

- Pseudodiploidy with translocations or molecular evidence of t(9;22),
11q23, or t(8;14) (excluding B-ALL) or +MLL gene rearrangement

- One of the following elevated WBC levels:

- WBC greater than 100,000/mm^3 if 6 to 12 months of age

- WBC greater than 200,000/mm^3 if between 10 and 17 years of age

- WBC greater than 20,000/mm^3 if 18 years of age and over (adult
[over 18 years of age] patient stratum closed to accrual)

- Failed to achieve CR after 4 weeks of induction therapy

- B-ALL that is not in first CR or that meets at least 1 of the high-risk
criteria specified above

- No translocation t(8;14)

- No blasts with surface immunoglobulins

- CD10 negative

- Undifferentiated leukemia*

- Infant leukemia*

- Biphenotypic leukemia*

- Chronic myelogenous leukemia, meeting 1 of the following criteria:

- Accelerated phase

- Chronic phase

- At least 1 year from diagnosis without an identified matched unrelated
bone marrow donor AND unresponsive to or unable to tolerate interferon

- Blast crisis* (greater than 30% promyelocytes plus blasts in the marrow)

- One of the following MDS:

- Refractory anemia

- Refractory anemia with ringed sideroblasts

- Refractory anemia with excess blasts (RAEB)

- RAEB in transformation

- Chronic myelomonocytic leukemia

- Paroxysmal nocturnal hemoglobinuria

- Hodgkin's or non-Hodgkin's lymphoma beyond first CR or failed primary induction
therapy

- Tumor displays chemosensitivity (greater than 50% reduction in mass size
after the most recent therapy) NOTE: *Patients in third or greater
medullary relapse or refractory disease (other than primary induction
failures) or blast crisis receive the study busulfan/melphalan conditioning
regimen)

OR

- Diagnosis of one of the following nonmalignant diseases :

- Acquired severe aplastic anemia (stratum closed to accrual)

- Unresponsive to medical therapy with anti-thymocyte globulin and/or
cyclosporine

- Inborn errors of metabolism, including, but not limited to the following:

- Hurler's syndrome

- Adrenoleukodystrophy

- Maroteaux-Lamy syndrome

- Globoid cell leukodystrophy

- Metachromatic leukodystrophy

- Fucosidosis

- Mannosidosis

- Fanconi anemia documented by increased chromosomal fragility assays and meeting
1 of the following criteria (stratum closed to accrual):

- Severe pancytopenia

- Absolute neutrophil count less than 500/mm^3

- Platelet count less than 20,000/mm^3

- Hemoglobin less than 8 g/dL

- Morphologic evidence of MDS with clonal chromosomal abnormalities

- Leukemia transformation

- Other marrow failure syndromes, including any of the following (stratum closed
to accrual):

- Blackfan-Diamond syndrome that is unresponsive to medical therapy

- Kostmann's congenital agranulocytosis unresponsive to medical therapy

- Congenital amegakaryocytic thrombocytopenia

- Thrombocytopenia absent radius

- Combined immune deficiencies including, but not limited to the following:

- Severe combined immunodeficiency (SCID)

- Wiskott-Aldrich syndrome

- Leukocyte adhesion defect

- Chediak-Higashi disease

- X-linked lymphoproliferative disease

- Adenosine deaminase deficiency

- Purine nucleoside phosphorylase deficiency

- X-linked SCID

- Common variable immune deficiency

- Nezeloff's syndrome

- Cartilage hair hypoplasia

- Reticular dysgenesis

- No active CNS leukemia (cerebrospinal fluid with WBC greater than 5/mm^3 and
malignant cells on cytospin)

- No SCID patients who do not require cytoreduction

- No dyskeratosis congenita

- No primary myelofibrosis

- No grade 3 or greater myelofibrosis

- Familial erythrophagocytic lymphohistiocytosis patients must not have any of the
following:

- Abnormal brain MRI

- Neurologic symptoms

- Lymphocytes and monocytes greater than 7/mm^3 in the cerebrospinal fluid

- No available 5/6 or 6/6 HLA-matched related donor

PATIENT CHARACTERISTICS:

Age

- 55 and under (over 18 closed to accrual)

Performance status

- Karnofsky 70-100% OR

- Lansky 50-100% (patients under 16 years old)

Life expectancy

- Not specified

Hematopoietic

- See Disease Characteristics

Hepatic

- SGOT less than 5 times upper limit of normal

- Bilirubin less than 2.5 mg/dL

Renal

- Creatinine normal for age OR

- Creatinine clearance or glomerular filtration rate greater than 50% of lower limit of
normal

Cardiovascular

- LVEF greater than 40% at rest and must improve with exercise* OR

- Shortening fraction greater than 26%* NOTE: *If symptomatic

Pulmonary

- DLCO greater than 45% of predicted* (corrected for hemoglobin)

- FEV_1 and FEC greater than 45% of predicted (corrected for hemoglobin) OR

- Room air oxygen saturation greater than 85%* NOTE: *If symptomatic

Other

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception

- No uncontrolled viral, bacterial, or fungal infection

- HIV negative

PRIOR CONCURRENT THERAPY:

Biologic therapy

- See Disease Characteristics

- More than 12 months since prior allogeneic stem cell transplantation with
cytoreductive preparative therapy

- More than 6 months since prior autologous stem cell transplantation

Chemotherapy

- See Biologic therapy

Endocrine therapy

- Not specified

Radiotherapy

- Not specified

Surgery

- Not specified

Other

- No prior enrollment on this study

- No continuous life support (e.g., mechanical ventilation) within 1 year after study
transplantation (for patients with inborn errors of metabolism)