Abstract
Aplastic anemia (AA) is a rare hematopoietic stem-cell disorder that results in pancytopenia and hypocellular bone marrow. The pathophysiology of acquired AA is immune-mediated in most cases. Activated type 1 cytotoxic T cells mediate the destruction of hematopoietic stem cells. The aberrant immune response and deficiencies in hematopoietic cells is now elucidated by molecular studies. In recent days, either stem cell transplant or immunosuppressive drug therapy with better supportive care has greatly improved the outcomes of patients with otherwise fatal disease. Combined immunosuppression with antithymocyte globulins and cyclosporine are effective in restoring blood counts in the majority of patients, but relapse and clonal evolution remain problematic. Allogeneic stem cell transplantation from matched sibling donors is curative in the great majority of young patients with severe AA. However, the results in patients who are older or lack family donors have room for improvement. Recent transplant results from alternative donors using a variety of conditioning regimens to enhance engraftment have been promising, especially in certain pediatric series.
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