Aplastic Anemia

Aplastic anemia is a disease of the bone marrowó 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. The patient\'s and the donor\'s marrow types must also match to minimize