Inclusion Criteria:

- Patients with dyskeratosis congenita (DC) or severe aplastic anemia (SAA) 0-70 years
of age with an acceptable hematopoietic stem cell (HSC) donor

- HSC source

- HLA identical or 1 antigen mismatched sibling or other relative eligible to
donate bone marrow (BM), umbilical cord blood (UCB) or mobilized peripheral
blood (PB) at cell doses that meet current institutional standards.

- HLA identical or up to a 1 antigen mismatched unrelated donor.

- Two units of unrelated umbilical cord blood (UCB) that are (a) up to 2 HLA
antigens mismatched to the patient (b) up to 2 HLA antigens mismatched to
each other, (c) minimum cell dose of ≥ 3.5 x 10^7 nucleated cells/kg and
optimal cell dose ≥ 5 x 10^7 nucleated cells/kg.

- If two units are not available: single unrelated UCB unit selected
according to Minnesota Bone Marrow Transplant (BMT) program guidelines

- Disease Characteristics for DC (both of the following):

- Evidence of BM failure:

- Requirement for red blood cell and/or platelet transfusions,

- Requirement for granulocyte colony-stimulating factor (G-CSF) or
granulocyte-macrophage colony-stimulating factor (GM-CSF) or
erythropoietin, or

- Refractory cytopenias defined as two out of three: platelets
<40,000/uL or transfusion dependent, Absolute neutrophil count <500/uL
without hematopoietic growth factor support, Hemoglobin <9g/uL or
transfusion dependent

- Diagnosis of DC:

- A triad of mucocutaneous features: oral leukoplakia, nail dystrophy,
abnormal reticular skin hyperpigmentation.

- Or one of the following: Short telomeres (under a research study),
Dyskerin mutation, TERC mutation

- Disease Characteristics for SAA (both of the following):

- Evidence of BM failure:

- Refractory cytopenia defined by bone marrow cellularity <25-50% (with
< 30% residual hematopoietic cells)

- Diagnosis of SAA:

- Refractory cytopenias defined as two out of three: Platelets
<20,000/uL or transfusion dependent, Absolute neutrophil count <500/uL
without hematopoietic growth factor support, Absolute reticulocyte
count <20,000/uL

- Patients with early myelodysplastic features.

- Patients with or without clonal cytogenetic abnormalities.

Patient Exclusion Criteria:

- Patients with one or more of the following:

- Decompensated congestive heart failure; left ventricular ejection fraction <35%

- Acute hepatitis or evidence of moderate or severe portal fibrosis or cirrhosis
on biopsy

- Carbon Monoxide Diffusing Capacity (DLCO) <30% predicted, and oxygen requirement

- Glomerular filtration rate (GFR) <30% predicted

- Pregnant or lactating female

- Active serious infection whereby patient has been on intravenous antibiotics for
at least one week prior to study entry. Any patient with AIDS or HIV
seropositivity. If recent mold infection e.g. Aspergillus - must have >30 days
of appropriate treatment before HSC transplantation and infection must be
controlled and cleared by the Infectious Disease consultant.

- Cannot receive TBI due to prior radiation therapy

- Diagnosis of Fanconi anemia based on diepoxybutane (DEB).

- DC patients with advanced myelodysplastic syndrome (MDS) or acute myeloid
leukemia with >30 blasts.

- History of non hematopoietic malignancy within 2 years except resected basal
cell carcinoma or treated carcinoma in situ.