The treatment strategy of Aplastic anemia (AA) is based on consideration of the severity of the disease (i.e. a high probability of demise), data on the response rate to different kinds of treatment options and the natural history of disease. Probable aspects of clinical reasoning, as reflected by benefit/risk estimates, highly dominate clinical strategies in AA. Patients with severe AA should be treated immediately. Of those patients who die, the majority will die during the first 4 months and/or during the first two years (approximately 60%).

The natural history of the disease is characterized by the development of late hematological complications such as acute leukemia, paroxysmal nocturnal hemoglobinuria (PNH) etc. Interestingly, this incidence has risen from 5-15% to more than 57% in those patients treated with immunosuppressive therapy; these factors should be taken into account when treatment is planned.

Initially, supportive therapy is of utmost importance, and early institution of antibiotics is critical in these patients. Platelets should be kept > 20,000/mm3. Granulocyte-macrophage colony-stimulating factors (GM-CSF), interleukin 3 (IL-3) and other growth factors will play an increasingly significant role during treatment of the aplastic phase of the disease.

The treatment of choice for young patients (<20 years old) with an HLA-compatible donor is bone-marrow transplantation (BMT). A candidate for BMT, if not transfused, has a long-term survival rate of over 75-80%, as compared with 40-65% for previously transfused patients. Therefore, if possible, one should avoid transfusion in BMT candidates.

The second line of treatment for patients with AA is immunosuppressive therapy (IST) with antithymocyte or antilymphocyte globulin (ATG or ALG) and/or cyclosporine. Although response rates as high as 85% have been reported, the true response rate to ATG seems to be between 40-60%. An analysis of data from the European registry indicated that for patients older than 20 years with moderately severe AA (those patients with 200-500 granulocytes/mm3, IST may be superior form of therapy. However, given the increased risk of a clonal disorder after IST, but not after BMT, BMT can still be the preferred option for patients between 20-45 years of age if estimated long-term survival after IST is less than 52%. One should be aware that complete normalization of the blood count with any form of therapy is not usual. Long term follow up indicates that after 10 years, 85% of patients had a normal blood cell count, 80% of patients had normal neutrophils, and 66% a normal platelet count. Late spontaneous improvements are also possible.