Aplastic anemia (AA) is a disease in which the bone marrow does not make enough blood cells. The three types of blood cells the body needs are red blood cells to carry oxygen, white blood cells to fight infections and platelets to control bleeding. When all three types of blood cells are very low, the person has severe aplastic anemia (SAA).
SAA is rare in the United States and Western Europe with an incidence of 3 cases per million per year and about 15 cases per million per year in East Asia. It can affect people of any age, but it is most common in young adults. In most cases the disease etiology is unknown. However AA may be the result of a variety of causes including ionizing radiation, benzene, and chemotherapeutic agents. Drugs causing marrow injury include chloramphenicol, phenylbutazone, sulfonamides, gold and specific anticonvulsants. Rarely, AA is associated with viral diseases such as non-A, non-B, non-C hepatitis.
Effective therapies consist of either immunosuppressive therapy with agents such as antithymoctye globulin or allogeneic hematopoietic cell transplantation. Studies have consistently shown a clear survival benefit for patients who received a matched sibling transplant compared to those who received immune suppressive therapy (IST).
Thus, for the SAA patient with ah HLA matched sibling donor, allogeneic transplant is the treatment of choice early after diagnosis. The use of unrelated donors has been challenging, but results of a National Marrow Donor Program study showed improved outcome with a conditioning regimen using low dose TBI, cyclophosphamide and anti-thymocyte globulin (ATG) and fully HLA matched donor by high-resolution DNA-based typing have superior outcome compared to IST. Thus, if a high-resolution 10 of 10 HLA-allele matched donor is identified, unrelated donor transplant should be considered early in the course of the treatment of patients with SAA, particularly for patients less than 20 years of age.
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