Aplastic Anemia
What is Aplastic Anemia?
Aplastic anemia is a blood disorder in which there is a failure of the bone marrow to produce sufficient blood cells for the circulation. Blood cells come from special cells in the bone marrow, called stem cells. Less than 1/5000 of the marrow cells is a stem cell. The stem cells give rise to a progressively maturing series of different cell types which eventually lead to all the functional blood cells found in the circulation. In aplastic anaemia blood production by stem cells fails resulting in a lack of red cells (anaemia), white cells (leading to an increased risk of infection) and platelets (which are needed to prevent bleeding and bruising). Aplastic anaemia is not a form of cancer. There is a lack of cells within the blood and the bone marrow shows replacement of normal blood forming cells with fat cells. Any remaining cells look more or less normal in contrast to leukemia or other blood cancers.
In aplastic anemia, your body stops producing enough new blood cells. This means you're fatigued and at higher risk of infections and uncontrolled bleeding. A rare and serious condition, aplastic anemia can develop at any age. Treatment for aplastic anemia may include medications, blood transfusions or a bone marrow transplant.
What are the types of aplastic anaemia?
Aplastic anemia can be inherited or acquired. Acquired aplastic anemia is much more common than the inherited type.
Inherited aplastic anemia. There are a number of rare inherited diseases which develop into bone marrow failure with a fatty marrow and loss of circulating blood cells. The most common is called Fanconi Anemia . There is wide variation in the presentation of this type of aplastic anaemia but it is usually fairly easy to differentiate it from acquired aplastic anaemia. Fanconi anaemia affects brothers and sisters within a family whereas the parents have normal blood counts. Typically the children are rather short and have abnormalities of the forearms or hands and a gradual but progressive failure of the bone marrow. The aplastic phase usually develops in childhood but may not present until adolescence or even early adult life.
Another inherited cause of aplastic anemia is called dyskeratosis congenita. Defects in some of the genes that help protect the chromosomes cause this disease. The chromosomes in our cells are fitted with caps at each end called telomeres. These caps help protect the ends of the chromosomes from being damaged. Telomerase is the protein that maintains the telomeres. Two different genes, called TERC and TERT, are needed to make telomerase. An abnormal copy of either one of these genes can cause dyskeratosis congenita. Another gene, DKC1, makes a protein called dyskerin that is needed for telomerase to work. Abnormalities in this gene also cause dyskeratosis congenita. Symptoms of this disorder include abnormal skin pigmentation, abnormal nails, and white patches in the mouth (called leukoplakia). People with this problem have a high risk of developing aplastic anemia and certain cancers. People with dyskeratosis congenita have higher rates of cancer of the mouth and throat and cancer of the anus. Some people are only diagnosed with dyskeratosis congenita when they come in with aplastic anemia and are found to have abnormal telomerase genes.
The third aplastic anemia is Blackfan Diamond anemia, the body's bone marrow produces little or no red blood cells. Blackfan Diamond anemia affects approximately 600 to 700 people worldwide. Its cause is unknown, although a genetic error in a gene called RPS19 on chromosome 19 is associated with about 25% of cases. In about 10% to 20% of cases, there is a family history of the disorder.
Acquired aplastic anemia usually occurs in adults, although children may also be affected. Most have no gene abnormalities. Scientists have found that some of the people who they thought had acquired aplastic anemia actually have an abnormality in one of the genes responsible for inherited aplastic anemia. The aplastic anemia in these people is not really acquired, because it is inherited.
Most individuals (80%) have acquired aplastic anemia, meaning that it was caused by infections such as hepatitis or Epstein-Barr virus, toxic exposure to radiation and chemicals, or drugs such as chloramphenical or phenylbutazone. Research suggests aplastic anemia may be the result of an autoimmune disorder.
Severity of aplastic anemia
Aplastic anemia can begin suddenly or develop slowly. It tends to get worse over time, except when a cause can be found and removed. Its severity ranges from mild to very severe. People with mild or moderate aplastic anemia have low blood counts that the doctor will check often. If the blood counts do not get worse, treatment may not be needed.
People with severe aplastic anemia have very low blood counts. Patients with SAA can be pale, and may experience fatigue (due to lower than normal red blood cells), infections (due to lower than normal white blood cells) and increased bruising and bleeding (due to lower than normal platelets). The condition can become life threatening if it is not treated. Although aplastic anemia is not cancer, the treatments for it are similar to those used for some types of cancer. Treatments include blood transfusions and bone marrow transplants. Treatments also include medicines to suppress the immune system, stimulate the bone marrow, and treat infections.