This suggests that cytokine‐induced and Fas‐mediated apoptosis play roles in bone marrow failure because annihilation of CD34+ progenitor cells leads to hematopoietic stem cell deficiency. Frequently detected autoantibodies
A study of blood and bone marrow samples obtained from 18 aplastic anemia patients revealed more than 30 potential specific candidate autoantigens after the serologic screening of a fetal liver library with sera from 8 patients. The human fetal liver cDNA library (chosen because of its high enrichment of CD34+ cells), compared with peripheral blood or the bone marrow, significantly increased the likelihood of detection of possible stem cell autoantigens. ELISA and Western blot analysis revealed that an IgG antibody response to one of the candidate autoantigens, kinectin, was present in a significant number of patients (39%). In contrast, no antibody was detected in 35 healthy volunteers. Antibody was detected in both transfused and transfusion-naive patients, suggesting that antikinectin autoantibody development was not due to transfusion-related alloreactivity. Negative sera from patients with other autoimmune diseases (systemic lupus erythematosus, rheumatoid arthritis, and multiple sclerosis) showed a specific association of antikinectin antibodies with aplastic anemia. These results support the hypothesis that immune response to kinectin may be involved in the pathophysiology of the disease. Kinectin is a large molecule (1,300 amino acid residues) expressed by CD34+ cells. Several kinectin-derived peptides can be processed and presented by HLA I and can induce antigen-specific CD8+ T-cell responses. Bone marrow microenvironment
A critical factor for healthy stem cell production is the bone marrow microenvironment.
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.