Submitted March 22, 2006
Accepted May 30, 2006
Current concepts in the pathophysiology and treatment of aplastic anemia
Neal S Young*, Rodrigo T Calado, and Phillip Scheinberg
Hematology Branch, National Heart, Lung, and Blood Institute, NIH, Bethesda, MD, USA
* Corresponding author; email: youngns{at}mail.nih.gov.
Aplastic anemia, an unusual hematologic disease, is the paradigm of the human bone marrow failure syndromes. Almost universally fatal just a few decades ago, aplastic anemia can now be cured or ameliorated by stem cell transplant or immunosuppressive drug therapy. The pathophysiology is immune-mediated in most cases, with activated type 1 cytotoxic T cells implicated. The molecular basis of the aberrant immune response and deficiencies in hematopoietic cells is now being defined genetically; examples are telomere repair gene mutations in the target cells and dysregulated T cell activation pathways. Immunosuppression with antithymocyte globulins and cyclosporine are effecctive at restoring blood cell production in the majority of patients, but relapase and especially evolution of clonal hematologic diseases remain problematic. Allogeneic stem cell transplantation from histocompatible sibling donors is curative in the great majority of young patients with severe aplastic anemia; the major challenges are extending the benefits of transplant to patients who are older or who lack family donors. Recent results with alternative sources of stem cells and a variety of conditioning regimens to achieve their engraftment have been promising, with survival in small pediatric case series rivaling conventional transplant results.
