• Donor cell engraftment [ Designated as safety issue: No ]
  
• Complete donor hematopoietic chimerism as assessed by short tandem repeats by PCR on week 2, 4 (or 1 month), 6, 8 (or 2 months), 12 (or 3 months), and 24 (or 6 months) after transplantation [ Designated as safety issue: No ]
  
• Event-free survival [ Designated as safety issue: No ]
  
• Overall survival [ Designated as safety issue: No ]
  

• Regimen-related toxicities as assessed by NCI's Common Toxicity Criteria [ Designated as safety issue: Yes ]
  
• Acute and chronic graft-versus-host disease [ Designated as safety issue: Yes ]
  
• Post-transplant immune reconstitution as assessed by lymphocyte subset, natural killer cell, and antibody counts on days 30, 60, 90, 180, and 365 after transplantation [ Designated as safety issue: No ]
  

OBJECTIVES:

• To evaluate the efficacy of HLA-haploidentical familial donor hematopoietic stem cell transplantation after reduced-intensity conditioning regimen comprising busulfan, fludarabine phosphate, and anti-thymocyte globulin in patients with bone marrow failure syndromes.

OUTLINE:

• Reduced-intensity conditioning regimen: Patients receive busulfan IV daily on days -7 and -6, fludarabine phosphate IV over 30 minutes on days -7 to -2, anti-thymocyte globulin (ATG) IV over 4 hours on days -4 to -1, and methylprednisolone IV over 30 minutes starting 30 minutes before ATG on days -4 to -1.
• HLA-haploidentical donor hematopoietic stem cell transplantation: Patients receive donor hematopoietic stem cells via Hickman catheter over 1 hour on days 0 or 1.
• Graft-versus-host-disease prophylaxis (GVHD): Patients receive cyclosporine IV over 2-4 hours every 12 hours starting on day -1 (cyclosporine can be given orally once oral medication can be tolerated) and methotrexate IV on days 2, 4 , 7, and 12. In the absence of GVHD, cyclosporine is tapered starting between days 30 to 60.

After completion of study treatment, patients are followed periodically for 1 year.

DISEASE CHARACTERISTICS:

• Diagnosis of any of the following bone marrow failure syndromes:

  • Severe aplastic anemia, meeting 1 of the following criteria:

    • Not responsive to immunosuppressive therapy
    • With recurrent cytopenia after immunosuppressive therapy or allogeneic hematopoietic cell transplantation

  • Low-risk myelodysplastic syndrome, including any of the following:

    • Refractory anemia
    • Refractory anemia with ringed sideroblasts
    • Refractory cytopenia with multi-lineage dysplasia

  • Paroxysmal nocturnal hemoglobinuria, meeting 1 of the following criteria:

    • With thrombotic episodes
    • With severe cytopenia

• No willing, suitable HLA-compatible donor in family or in donor registries

  • Related donor with HLA-haploidentical mismatch at three or less of 6 loci
  • Patients with very severe neutropenia (< 200/μL) or febrile episodes, who feel urgent need for allogeneic hematopoietic cell transplantation, are eligible without a search for HLA-matched unrelated donors

PATIENT CHARACTERISTICS:

• Karnofsky performance status 70-100%
• Bilirubin < 2.0 mg/dL
• AST < 3 times upper limit of normal
• Creatinine < 2.0 mg/dL
• Ejection fraction > 40% by MUGA scan

PRIOR CONCURRENT THERAPY:

• See Disease Characteristics