Management of Acquired Aplastic Anemia

Acquired aplastic anemia is an uncommon disorder of unknown pathogenesis characterized by peripheral blood pancytopenia and a hypocellular marrow, where normal hematopoietic tissue is replaced by fat cells. About 15% of cases follow exposure to drugs or a hepatitic-like illness. The differential diagnosis includes congenital aplastic anemia, myelodysplastic syndrome (MDS) or leukemias presenting with hypocellular phase and, rarely, antibody-mediated pancytopenias. Support with blood products and the avoidance and treatment of infection provide the essential platform for more definitive therapy. Allogeneic stem cell transplantation from a human leukocyte antigen (HLA)-matched sibling donor is the most appropriate first-line treatment for children and young adults (< 45 years of age) with severe or very severe aplastic anemia. Immunosuppression with antilymphocyte globulin or antithymocyte globulin followed by cyclosporine is the most appropriate treatment for the remaining patients. The response to therapy is determined mainly by the severity of the disease and is independent of the etiology. Immunosuppressive therapy is equally effective in older patients as in younger. Sibling transplantation is successful in 70–90% of cases — the results seem to improve year by year. About two out of three patients respond to a first course of immunosuppressive therapy, but relapse or late complications occur in 25–40% of patients so treated over 10 years. In patients who do not respond to the first course of immunosuppression, subsequent courses can be given with the expectation of success, although the response is slow. Late complications include the emergence of abnormal clones, e.g. paroxysmal nocturnal hemoglobinuria, MDS and acute leukemia. The place of stem cell transplantation from unrelated volunteer donors has yet to be properly defined.