Many patients with aplastic anemia also have clones of cells characteristic of paroxysmal nocturnal hemoglobinuria (PNH), a rare disease that causes anemia with thrombocytopenia and/or thrombosis and is sometimes referred to as AA/PNH. Occasionally PNH dominates over time, with the major manifestation of intravascular hemolysis. The overlap of AA and PNH has been speculated to be an escape mechanism by the bone marrow against destruction by the immune system. Flow cytometry testing is performed regularly in people with previous aplastic anemia to monitor for the development of PNH. Prognosis
Untreated, severe aplastic anemia has a high risk of death. Modern treatment produces a five-year survival rate that exceeds 85%, with younger age associated with higher survival.Survival rates for stem cell transplants vary depending on the age and availability of a well-matched donor. They are better for patients who have donors that are matched siblings and worse for patients who receive their marrow from unrelated donors. Overall, the five-year survival rate is higher than 75% among recipients of blood marrow transplantation.Older people (who are generally too frail to undergo bone marrow transplants) and people who are unable to find a good bone marrow match have five-year survival rates of up to 35% when undergoing immune suppression.Relapses are common. Relapse following ATG/ciclosporin use can sometimes be treated with a repeated course of therapy. In addition, 10–15% of severe aplastic anemia cases evolve into myelodysplastic syndrome and leukemia. According to one study, 15.9% of children who responded to immunosuppressive therapy eventually relapsed.Milder disease may resolve on its own.
It is not a hereditary condition, nor is it contagious.Aplastic anemia is also sometimes associated with exposure to toxins such as benzene or with the use of certain drugs, including chloramphenicol, carbamazepine, felbamate, phenytoin, quinine, and phenylbutazone. However, the probability that these drugs will lead to aplastic anemia in a given patient is very low. Chloramphenicol treatment is associated with aplasia in less than one in 40,000 treatment courses, and carbamazepine aplasia is even rarer.Exposure to ionizing radiation from radioactive materials or radiation-producing devices is also associated with the development of aplastic anemia. Marie Curie, famous for her pioneering work in the field of radioactivity, died of aplastic anemia after working unprotected with radioactive materials for a long period of time; the damaging effects of ionizing radiation were not then known.Aplastic anemia is present in up to 2% of patients with acute viral hepatitis.One known cause is an autoimmune disorder in which white blood cells attack the bone marrow. Acquired aplastic anemia is a T-cell mediated autoimmune disease, in which regulatory T cells are decreased and T-bet, a transcription factor and key regulator of Th1 development and function, is upregulated in affected T-cells. As a result of active transcription of the interferon gamma (IFN-gamma) gene by T-bet, IFN-gamma levels are increased, which reduces colony formation of hematopoietic progenitor cells in vitro by inducing apoptosis of CD34+ cells in the bone marrow.Short-lived aplastic anemia can also be a result of parvovirus infection.