Bone marrow transplantation for aplastic anemia

Abstract

Aplastic anemias are congenital or acquired clinical disorders characterized by cytopenia of peripheral blood associated with a hypocellular bone marrow not infiltrated by other abnormal tissues or fibrosis. The degree of pancitopenia, particularly thrombocytopenia and granulocytopenia, establishes the prognosis. Severe Aplastic Anemia (SAA) is the most frequent entity of this group of diseases and its treatment involves supportive measures, immunosuppressive therapy (IT) and bone marrow transplantation (BMT). Supportive treatment is of major importance to prevent serious and fatal complications, particularly bleeding and infections. The choice of the definitive therapy is based in the age of the patient, disease severity and obviously the availability of an HLA identical sibling marrow donor. BMT is indicated for patients with SAA younger than 20 years, for high risk patients between the ages 20-40 and for other patients who did not respond to IT. Blood transfusions previous to BMT are an adverse factor, since in patients less transfused (<15 units), the long term disease free survival is more than 90%, and for those heavily transfused it drops to 65%. Syngeneic (identical twin) transplants are successful, however have specific characteristics. The utilization of an unrelated marrow donor for BMT in SAA is possible but it is still considered experimental. Fanconi Anemia (FA) is the most common hereditary aplastic anemia in which BMT is able to restore a normal hematopoiesis. FA patients are extremely sensitive to alkylating agents and irradiation and a specific preparative regimen for BMT was developed to avoid unacceptable toxicity. Currently, complete hematologic recovery occurs in more than 80% of FA patients after an HLA-identical sibling allogeneic BMT. The results of unrelated bone marrow donor transplantation in FA are still poor. Dyskeratosis Congenita, Blackfan-Diamond Anemia and Hereditary Thrombocytopenias are other forms of hereditary aplasias in which BMT is able to fully correct the hematological abnormalities.