Aplastic Anemia Essays - Transplantation Medicine, Stem Cells

Aplastic Anemia Aplastic anemia is a disease of the bone marrow the organ that produces the body's blood cells. Approximately two thousand people in the U.S. are diagnosed each year with aplastic anemia. The symptoms of aplastic anemia are fatigue, bruising, infections, and weakness. Although these symptoms are much like those associated with leukemia, aplastic anemia is not a form of cancer. In patients with aplastic anemia the bone marrow stops producing, or produces too few red blood cells, white blood cells, and platelets. Without sufficient red blood cells, oxygen cannot reach organs and tissues throughout the body. A decrease in the number of white blood cells causes the body's ability to fight infection as well as it should. Platelets are needed to help blood clot (Bone). Although the exact cause of aplastic anemia is not known, most evidence points to a combination of factors. The first factor is damaged stem cells. These are the primitive cells in the bone marrow that produce blood cells. Another factor is damage to the bone marrow environment in which blood cells develop (Aplastic). Other factors include abnormalities in the proteins that regulate blood cell production and a malfunctioning immune system that interferes with the normal blood cell production (Bone). Certain environmental factors have been associated with the development of aplastic anemia. Chemotherapy drugs such as busulfan or antibiotics such as chloraphenicol can cause temporary or prolonged aplastic anemia. Chemicals such as benzene and pesticides, infections such as viral hepatitis and mononucleosis, autoimmune disorders and ionizing radiation also have been linked to the development of aplastic anemia. Although exposure to these agents increases the risk of developing aplastic anemia, it is proven that they are not the sole cause of aplastic anemia (Aplastic). Aplastic anemia was once considered incurable. Today, more than fifty percent of patients diagnosed with aplastic anemia can be cured. For patients under the age of fifty and those over fifty that are in good health, the treatment of choice is a bone marrow transplant (National). However, more than half of the patients that are diagnosed are ineligible foe a bone marrow transplant because of age or the lack of a suitable bone marrow donor. For these patients, the preferred treatment is immunosuppressive therapy consisting of injections of antithymocyte globulin (ATG), with or without oral closporine. ATG therapy boosts the production of red blood cells, blood cells, and platelets in thirty to fifty percent of patients. In some cases, blood cell production returns to normal, while in others it returns to a level that allows the patient to have a normal lifestyle (Aplastic). Approximately ten to fifteen percent of patients who initially respond to ATG therapy have the disease relapse during the first twelve months following treatment. Another round of ATG therapy may be administered in an effort to bring blood cell production back to an acceptable level. Some patients who respond to ATG therapy eventually develop another bone marrow disorder such as myelogenous syndrome or acute nonmyelogenous leukemia. These disorders may be temporarily treatable, but are seldom curable. Overall, between thirty and forty percent of patients treated with ATG therapy become long term survivors and the majority of these long term survivors appear to be cured (Aplastic). Patients who have a relative with matching bone marrow have a seventy to ninety percent chance of being cured following a bone marrow transplant. Patients transplanted with marrow from a related donor whose marrow type nearly matches the patient's have a fifty percent chance of being cured. If marrow from a matched unrelated donor is used, the likelihood of a cure is twenty to thirty percent (Bone). Physicians determine whether a donor's marrow type matches the patient's by examining genetic markers on the surface of white blood cells called HLA antigens. These are the antigens that help the body identify invading organisms, and trigger an immune system attack on any substances that do not belong in that particular person's body, such as viruses and bacteria (Severe). If the patient's and donor's HLA antigens do not match, the patient's body will perceive the donor's bone marrow as foreign material to be destroyed. This condition is called graft rejection and results in a failed bone marrow transplant.