DISEASE CHARACTERISTICS:

• Histologically confirmed diagnosis of severe aplastic anemia based on bone marrow cellularity of less than 20%

• Must meet at least two of the following criteria:

  • Granulocyte count less than 500/mm^3
  • Platelet count less than 20,000/mm^3
  • Reticulocyte count less than 50,000/mm^3

• Following etiologies eligible:

  • Fanconi's anemia
  • Hypoplastic leukemia
  • Monosomy 7
  • Drug exposure (chloramphenicol, NSAIDS)
  • Viral exposure (EBV, hepatitis, parvovirus, HIV)
  • Nutritional deficiencies
  • Thymoma
  • Paroxysmal nocturnal hemoglobinuria
  • Amegakaryocytic thrombocytopenia OR
• Histologically confirmed myelodysplastic syndrome (MDS) that is refractory to medical management or with cytogenic abnormalities predictive of transformation into acute leukemia, including 5q-, 7q-, monosomy 7, or trisomy 8

• The following etiologies only are eligible:

  • Refractory anemia
  • Refractory anemia with ringed sideroblasts
  • De novo primary MDS
  • Therapy-related secondary MDS OR
• Confirmed diagnosis of inherited hematopoietic disorder that is refractory to medical management

• Following etiologies eligible:

  • Severe combined immunodeficiency
  • Familial erythrophagocytic lymphohistiocytosis
  • Wiskott-Aldrich syndrome
  • Kostmann's syndrome (infantile histiocytosis)
  • Chronic granulomatous disease
  • Leukocytic adhesion deficiency
  • Chediak-Higashi syndrome
  • Paroxysmal nocturnal hemoglobinuria
  • Fanconi's anemia
  • Dyskeratosis congenita
  • Diamond-Blackfan anemia
  • Amegakaryocytic thrombocytopenia
  • Osteopetrosis
  • Gaucher's disease
  • Lesch-Nyhan syndrome
  • Mucopolysaccharidoses
  • Lipodoses
• Autologous or haploidentical related peripheral blood stem cells available as backup
• Serologically matched umbilical cord blood unit available in the New York Blood Center's Placental Blood Project, or other acceptable umbilical cord blood registry

PATIENT CHARACTERISTICS:

Age:

• 55 and under

Performance status:

• Zubrod 0-1
• Karnofsky 80-100%

Life expectancy:

• At least 3 months

Hematopoietic:

• See Disease Characteristics

Hepatic:

• ALT/AST no greater than 4 times normal
• Bilirubin no greater than 2.0 mg/dL

Renal:

• Creatinine no greater than 2.0 mg/dL
• Creatinine clearance at least 50 mL/min

Cardiovascular:

• Normal cardiac function by echocardiogram or radionuclide scan
• Shortening fraction or ejection fraction at least 80% normal for age
• Non-Fanconi patients with acquired or congenital cardiomyopathy may receive melphalan as a substitute for cyclophosphamide

Pulmonary:

• FVC and FEV_1 at least 60% of predicted for age
• DLCO at least 60% of predicted in adult patients

Other:

• No active concurrent malignancy
• No active infection
• Not pregnant or nursing
• HIV negative
• Must have an available serologic matched Umbilical Cord Blood Unit (UCBU) in the New York Blood Center's Placental Blood Project, or other acceptable Umbilical Cord Blood (UCB) registry

PRIOR CONCURRENT THERAPY:

Biologic therapy:

• Not specified

Chemotherapy:

• No concurrent cytotoxic chemotherapy

Endocrine therapy:

• No concurrent immunosuppressive medications

Radiotherapy:

• No concurrent radiotherapy

Surgery:

• Not specified