Umbilical Cord Blood Transplantation in Treating Patients With Hematologic Cancer or Other Hematologic or Metabolic Diseases

DISEASE CHARACTERISTICS: Histologically confirmed diagnosis of one of the following: - Severe aplastic anemia with bone marrow cellularity less than 20% and at least 2 of the following criteria: Granulocyte count less than 500/mm3 Platelet count less than 20,000/mm3 Reticulocyte count less than 50,000/mm3 Etiologies may be Fanconi's anemia, hypoplastic leukemia, monosomy 7, drug exposure (chloramphenicol, NSAIDS), viral exposure (EBV, hepatitis, parvovirus, HIV), nutritional deficiencies, thymoma, paroxysmal nocturnal hemoglobinuria, and amegakaryocytic thrombocytopenia - Myelodysplastic syndrome (MDS) that is refractory to medical management or with cytogenetic abnormalities predictive of transformation into acute leukemia, including 5q-, 7q-, monosomy 7, and trisomy 8 De novo primary or therapy-related secondary MDS Refractory anemia or refractory anemia with ringed sideroblasts only - Inherited hematopoietic disorders that are refractory to medical management Severe combined immunodeficiency Familial erythrophagocytic lymphohistiocytosis Wiskott-Aldrich syndrome Kostmann's syndrome (infantile agranulocytosis) Chronic granulomatous disease Leukocyte 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 Lipidoses Must also meet all the following conditions: No HLA-ABC/DR identica…