Severe aplastic anemia is a rare syndrome characterized by bone marrow failure with cytopenias and hypocellular bone marrow biopsy (usually 10-15%), without blasts or myelodysplasia. The first choice treatment for these patients is allogeneic bone marrow transplantation from a sibling matched for HLA-A, HLA-B and HLA-DR. Unfortunately only 30% of patients have an HLA-matched sibling (a 25% chance per sibling). The alternative treatment for severe aplastic anemia for the rest of the patients

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... ) is immunosuppression with antithymocyte globuline and cyclosporine. The evolution of bone marrow transplantation since 1970's has been positive in terms of survival and transplant success (initial overall survival 43% vs. 90% lately, and graft rejection of 29% vs. 4%). The favorable outcome of bone marrow transplantation for severe or very severe aplastic anemia is due to: the use of conditioning with antithymocyte globuline and cyclophosphamide, the use of graft-vs.-host disease prophylaxis with short curse methotrexate and cyclosporine and the use of filtrated and irradiated blood products. For those patients without an HLA-matched related donor the first treatment to use is the immunosuppression with antithymocyte globuline and cyclosporine. Another option emerged in the late 80's is the unrelated bone marrow transplantation, with survival hardly half of the HLA-identical related bone marrow transplants. In our country, the first allogeneic bone marrow transplant was done in the Instituto Nacional de Ciencias Médicas y Nutrición, Salvador Zubirán, in a patient with aplastic anemia, making possible to perform this procedure safely in our country.