Pilot Study Of Unrelated UCB Transplant for Non-Malignant Hematologic Conditions

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