Aplastic Anemia (A.A.) is a blood disorder in which the bone marrow is unable to produce an adequate amount of new blood cells. It is characterized by a condition known as pancytopenia, which means a decreased number of red blood cells, white blood cells and platelets. The bone marrow is a red, spongy substance inside of your bones. It is responsible for the production of stem cells. These stem cells produce the red blood cells, white blood cells and platelet. In Aplastic Anemia, the bone marrow is damaged.
Etiology or Causes
This condition can be inherited, which is rare, or acquired. The inherited form presents as a congenital, autosomal recessive disorder. When A.A. is acquired it is believed to be a result of an immune mediated response. In most cases, the cause is not known or idiopathic in nature. In other cases, there are several factors that can damage the bone marrow which results in a diminished production of stem cells. Those factors are viruses, chemotherapy and radiation, exposure to certain environmental toxins, medications, an autoimmune disorder, and pregnancy (believed to be related to an autoimmune response). The viruses that have been connected to the development of this disorder include cytomegalovirus, Epstein-Barr, hepatitis, HIV and parvovirus B19.
Signs and Symptoms
Symptoms related to a diminished supply of red blood cells are fatigue, dizziness, lightheadedness, fast and irregular heart beat, shortness of breath upon exertion, and pallor. Symptoms related to a diminished supply of white blood cells are frequent and prolonged infections. Symptoms related to a diminished supply of platelets are bruising easily, petechial skin rash, prolonged bleeding from cuts, and a propensity to nosebleeds and bleeding gums.
In order to make a definitive diagnosis, a blood test will be ordered. Typically, the red blood cells, white blood cells and platelet levels will fall within a set parameter. However, with A.A., all three of the levels will be low.
A bone marrow biopsy will be ordered. In this procedure, your doctor will numb the donor site by injecting some medication into it. He then will insert a small needle into the bone marrow and obtain a sample of bone marrow from a large bone, typically, the hip bone. The sample is examined under a microscope to determine if blood cell counts are low, as well as, look for the presence of other disease processes.
Treatment and Prevention
Treatment for Aplastic Anemia varies and is contingent upon the severity of the case. For mild cases, observation is ordered and symptoms are treated as they erupt. For cases that are more serious, a blood transfusion may be necessary to replenish whichever component is seriously diminished. While a blood transfusion may not be the cure for A.A., it will relieve some of the symptoms that accompany this disease.
To correct red blood cells deficiencies, a transfusion of packed red blood cells are given. Blood products that are irradiated or leukocyte depleted should be used because this will limit the exposure to the Human Leukocyte Antigens (HLA) should the child require bone marrow transplantation in the future. This will help to relieve the symptoms of fatigue, lightheadedness, dizziness and anemia. Units of platelets are transfused to correct the platelet deficiency and to control the excessive bleeding. The downside to this treatment is that with transfusions, there are potential complications. For example, transfused blood contains a lot of iron and although there is not a limit as to how many transfusions one may receive, this complication becomes more possible with the increase in the number received. The amount of iron will tend to accumulate in the blood. The good news, however, is that there is medication that can be prescribed to treat this condition by ridding the body of excess iron. Another complication with blood transfusion, is the body will develop antibodies as a natural response in receiving the donor’s blood. Consequently, the body will launch an immune response to receiving foreign blood. Immunosuppressing drugs can be prescribed to combat this complication.
Bone Marrow Transplantation
For those with severe A.A., a stem cell transplant may offer the only successful treatment option. A stem cell transplant, also known as, a bone marrow transplant is a multi-step process. The first step involves finding a person, a donor (often a sibling), who will agree to contribute their bone marrow stem cells to the diseased person. The donor will then be tested to determine if their stem cells will be a match to the recipients.
If the donor and the recipient share the same Human Leukocyte Antigens (abbreviated as HLA), they are said to be a “match.” This means that their tissues are immunologically compatible with each other. Next, the recipient’s bone marrow is depleted through radiation treatments and chemotherapy. Then, the donor’s stem cells are filtered from their blood and later injected intravenously into the recipient’s bloodstream. These healthy stem cells will migrate into the bone marrow cavities where they will begin producing new blood cells. This process involves a lengthy hospital stay and typically, the patient is placed in isolation.
There are risks involved with this procedure. The recipient may reject the transplanted stem cells which can lead to life-threatening complications. The treatment also may involve the use of drugs that will suppress the immune system. These drugs known as immune-suppressants, will aid in preventing the rejection of the donated stem cells.
For those in which the aplastic anemia was a result of an autoimmune disorder, the treatment may involve the use of immunosuppressant. Drugs like cyclosporine and anti-thymocyte globulin work by suppressing the activity of immune cells that are causing the damage to the bone marrow. Consequently, the bone marrow will be able to recover and produce new blood cells. Corticosteroid drugs are often used in adjunct to these immune suppressing drugs. Although, these drugs can be effective in treating this disorder, there is a downside to using these drugs. Since they will weaken your immune system it can make your body vulnerable to contracting an infection.
There are a number of drugs available that can be used to help stimulate the bone marrow to produce new blood cells, known as bone marrow stimulants. In light of a weakened immune system due to the drugs as well as a diminished amount of circulating white blood cells, the body will become susceptible to infections. At the first sign of infection, such as a fever, you should contact your doctor. Your doctor may prescribe an antibiotic or an antiviral drug.
Aplastic anemia, if left untreated, tends to get worse over time and has a high risk of death. However, if the cause for the disease is found and treatment is initiated, it can be successfully treated. The survival rate for those treated by stem cell transplantation varies and is dependent upon age and the degree of compatibility of the donor.
Obviously, the well-matched donor offers the best survival rate, particularly, if the donor is a sibling of the recipient in contrast to an unrelated donor. Studies has shown that the survival rate of those under the age of 20 are better than those over the age of twenty with the chances of survival within the 5 year window becoming less as one ages.