Реферат: Aplastic Anemia Essay Research Paper Aplastic anemia
Aplastic Anemia Essay, Research Paper
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 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
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 the risk and severity of another
complication called graft versus host disease (Bone).
The primary complication following a bone marrow transplant for aplastic anemia is graft versus host disease. In
graft versus host, the donor’s bone marrow attacks the patient’s organs and tissues, impairing their ability to function,
and increasing the risk of infection. Depending on its severity, graft versus host can be a temporary inconvenience or
a life threatening condition (Aplastic).
Graft versus host is often referred to as only one disease, but in reality it is actually two closely related diseases:
acute graft versus host disease and chronic graft versus host disease. Patients may develop one, both, or neither.
Acute graft versus host disease usually occurs within the first three months after the bone marrow transplant.
Chronic graft versus host disease usually develops after the third month following the transplant (National).
The earliest sign of acute graft versus host disease is often a skin rash that appears on the hands or feet. It may
spread to other parts of the body, developing into a general redness similar to a sunburn, with peeling or blistering
skin. Cramping, nausea, and watery or bloody diarrhea are also signs of acute graft versus host disease in the
stomach or intestines. Jaundice indicates that graft versus host has affected the liver (Severe).
Patients with chronic graft versus host disease usually experience skin problems such as a dry, itching rash, a change
in skin color, on tautness or tightening of the skin (Severe). Occasionally, patients will experience “contractures”,
which are the tightening of the tendons in the joints that makes extending or contracting arms and legs difficult.
Partial hair loss or premature graying may also occur (Aplastic).
Chronic graft versus host may also attack the glands in the body that secrete mucus, saliva and other lubricants.
Patients may experience dry or stinging eyes, a dry mouth or throat, and a burning sensation in the mouth when
using toothpaste or eating acidic foods. The digestive tract may be affected by chronic graft versus host disease,
causing heartburn, stomach pain, or weight loss. It may also affect the liver and lungs, causing wheezing, bronchitis,
or pneumonia (National).
To reduce the incidence and severity of acute graft versus host, patients are given immunosuppressive drugs. These
drugs are routinely administered for approximately six months after the bone marrow transplant and longer if the
patient develops chronic graft versus host disease (Aplastic).
The risk of developing acute graft versus host depends on the source of the bone marrow and the choice of
medications given to prevent it. Fifteen to thirty percent of patients transplanted with marrow from a related donor
develop acute graft versus host. In most cases, patients develop only a mild or moderate form of the disease.
Approximately seventy percent of patients transplanted from an unrelated donor develop the disease (Bone).
The risk of developing chronic host versus graft depends upon the source of the marrow and the age of the patient.
About thirty percent of the patients who receive marrow from a related donor develop the disease. About seventy
percent of the patients who receive marrow from an unrelated donor develop the disease (Severe).
Although most patients recover from graft versus host disease, symptoms such as skin sensitivity, eye irritation,
chronic diarrhea, and less frequently, lung and liver problems or contractures, may persist long term. Most patients,
however, do not experience long term debilitating side effects (Severe).
Some patients transplanted for aplastic anemia require a preparative regimen that includes total body irradiation
(TBI). Children given TBI have experienced slowed growth and hormone development, and are more likely to be
infertile than those whose preparative steps did not include TBI. Patients of all ages have a greater risk of
developing a secondary cancer following TBI than other patients. Still, the overall chance of having a secondary
cancer is very low (Aplastic).
Norma Ramsay of the University of Minnesota Hospitals states, “The treatment of severe aplastic anemia with bone
marrow transplantation is truly one of modern day medicine’s major success stories” (National). The treatment for
aplastic anemia has improved greatly over the past two decades. Prior to 1970, only ten percent of patients lived
more than a year after diagnosis. Now, approximately eighty percent of the patients are alive three to five years after