Risk-Adapted Allogeneic Stem Cell Transplantation For Mixed Donor Chimerism In Patients With Non-Malignant Diseases

Inclusion Criteria Patients must meet the eligibility criteria for organ function regardless of diagnosis: * Age \< 30 or = 30 years of age * Adequate renal function defined as serum creatinine \< or = 1.5 x normal, or creatinine clearance or radioisotope glomerular filtration rate (GFR) \> or =40 ml/min/m2 or \>60 ml/min/1.73 m2 or an equivalent GFR as determined by the institutional normal range * Adequate liver function defined as serum glutamic oxaloacetic transaminase (SGOT)(Aspartate transaminase (AST)) or serum glutamic-pyruvic transaminase (SGPT) (alanine aminotransferase (ALT)) \< 5.0 x normal * Adequate cardiac function defined as shortening fraction of \> or = 28% by echocardiogram, or ejection fraction of \> or = 48% by radionuclide angiogram or echocardiogram * Adequate pulmonary function defined as asymptomatic or, if symptomatic, carbon monoxide diffusing capacity test (DLCO) \>45% of predicted (corrected for hemoglobin level). If unable to obtain pulmonary function test, O2 saturation \>85% in room air. Bone Marrow Failure Syndromes Patients with the following diagnoses are eligible: Severe Aplastic Anemia: * Hypocellular bone marrow biopsy (\<25% cellularity) and 2/3 of the following (at diagnosis or nadir): * Absolute Neutrophil Count (ANC) \<200/mm3, * Platelets \<20,000/mm3 * Reticulocyte count \<60,000/mm3 Fanconi Anemia: * Abnormal clastogenic studies (all patients) Severe Congenital Neutropenia (Kostmann's Syndrome) Amegakaryocytic Thrombocytopenia * Severe thrombocytopenia (\< or =20,000/mm3) at diagnosis * Severe depletion of megakaryocytes on bone marrow aspirate (\< or =25% normal) Diamond-Blackfan Anemia: * Corticosteroid dependent for \> 6 months OR Transfusion dependent OR refractory acquired pure red cell aplasia. Infantile Osteopetrosis Schwachman-Diamond Syndrome Dyskeratosis Congenita Other bone marrow failure syndromes at discretion of co-principal investigators All BM failure patients must have BM bx within 2 weeks prior to starting therapy to confirm disease status Immunodeficiencies: * SCIDS, all subtypes * Combined Immunodeficiency Syndrome * Wiskott-Aldrich Syndrome * Chronic Granulomatous Disease * Chediak-Higashi Syndrome * Leukocyte Adhesion Deficiency * Other immunodeficiencies at discretion of co-principal investigators Inborn Errors of Metabolism (IEOM): Transplant is recommended for the following disorders: * Hurler syndrome (alpha-L-iduronidase deficiency, MPS-I), preferably before age 24 months * Maroteaux-Lamy syndrome (galactosamine-4-sulfatase deficiency,MPSVI) * Sly syndrome (beta-glucuronidase deficiency, MPS-VII) * Globoid cell leukodystrophy (galactocerebrosidase deficiency), with careful attention to neurologic status in the infantile form * Metachromatic leukodystrophy (arylsulfatase A deficiency),juvenile or adult onset form; late infantile MLD only if pre-symptomatic * Childhood-onset X-linked adrenoleukodystrophy (X-ALD), at initial signs of neuropsychological deterioration, with dietary modification prior to transplant * Fucosidosis (fucosidase deficiency) * Mannosidosis * Aspartylglucosaminuria * Niemann-Pick Disease Type B (acid sphingomyelinase deficiency) * Other diagnoses may be considered at the discretion of the co-principal investigators Transplant is not recommended for Hunter syndrome (iduronate sulfatase deficiency), Sanfilippo syndrome Type A (heparan N-sulfatase deficiency), Sanfilippo syndrome Type B (-N-acetyl-transferase deficiency), Sanfilippo syndrome Type C (-acetyltransferase deficiency), Sanfilippo syndrome Type D (-acetylglucosamine-6-sulfatase deficiency), Morquio syndrome (galactose-6-sulfatase deficiency); or Niemann-Pick disease Type A or C. For X-ALD patients greater than 5 years of age, IQ \>80 is required. For other patients greater than 5 years of age, IQ \> 70 is required. For patients less than 5 years of age, the developmental quotient or clinical neurodevelopmental examination should demonstrate potential for stabilization at a level of functioning where continuous life support (e.g. mechanical ventilation) would not be predicted to be required in the year following transplantation. For Gaucher disease (glucocerebrosidase deficiency) Type I (non-neuropathic), the primary therapy is enzyme replacement, but allogeneic stem cell transplant has been used effectively. Histiocytoses: * Hemophagocytic Lymphohistiocytosis (HLH) * Familial Erythrophagocytic Lymphohistiocytosis * Langerhans Cell Histiocytosis * Patients with multi-system disease whose initial disease is stable or progressive after minimum 6 weeks of appropriate therapy, OR patients with recurrent multi-system disease. * Malignant Histiocytosis * All histiocytic patients must have BM bx within 2 weeks prior to starting therapy to confirm disease status Other non-malignant diseases not listed above may be eligible if deemed appropriate by the co-principal investigators.