Allogeneic Hematopoietic Stem Cell Transplant for GATA2 Mutations

Background: \- GATA2 deficiency is a disease caused by mutations in the GATA2 gene. It can cause different types of leukemia and other diseases. Researchers want to see if a stem cell transplant can be used to treat this condition. A stem cell transplant will give stem cells from a matching donor (related or unrelated) to a recipient. It will allow the donor stem cells to produce healthy bone marrow and blood cells that will attack the recipient s cancer cells. Objectives: \- To see if stem cell transplants are successful at treating GATA2 mutations and related conditions. Eligibility: \- Recipients who are between 6 and 70 years of age and have GATA2 deficiency. Design: * All participants will be screened with a physical exam and medical history. Blood samples will be collected. Recipients will have imaging studies and other tests. * Recipients will have chemotherapy or radiation to prepare for the transplant. On the day of the transplant, they will receive the donated stem cells. * Recipients will stay in the hospital until their condition is stable after transplant. * Frequent blood tests and scans will be required for the first 6 months after the transplant, followed by less frequent visits over time.

* ELIGIBILITY CRITERIA: INCLUSION CRITERIA- Recipient 1. Patient age of 6-70 years. 2. Mutation in the GATA2 gene, or evidence of loss of expression of one allele of GATA2, by cDNA analysis performed by a CLIA certified laboratory, or the clinical syndrome of MonoMAC. 3. Clinical history of at least one serious or disfiguring infection and/or GATA2 bone marrow immunodeficiency disorder with lose of one or more immune populations in the bone marrow including monocytes, Natural Killer (NK) cells, and B-lymphocytes, with or without additional cytopenias involving the red blood cell, neutrophil, or platelet compartment. 4. Availability of a 10/10 or 9/10 or 8/10 HLA-matched related or unrelated donor, or a haploidentical related donor. 5. Patients may have evidence of MDS with one or more peripheral blood cytopenias and greater than 5% blasts but must have less than 10% blasts in the bone marrow in the absence of filgrastim in order to proceed directly to transplant. The majority of patients with MDS will have less than 5% blasts. 6. Disease status: Patients are to be referred in remission for evaluation. Should a patient have progressive disease with \>10% blasts on screening/baseline bone marrow biopsy, the patient may receive standard treatment under the current study prior to proceeding with transplant. Once the patient has \ 40%, preferably by 2-D echocardiogram obtained within 90 days prior to initiation of conditioning therapy. 8. Creatinine: Adult patients: \= 30 ml/min; Pediatric patients (\