Aplastic anemia is a disease that affects the bone marrow and the blood stem cells that reside there. It leads to a deficiency of all the three types of blood cells.
Aplastic anemia is a type of anemia where the body’s bone marrow does not produce sufficient red blood cells, white blood cells, and platelets. This condition can occur due to some problem either specifically in the bone marrow, or due to a systemic disease that is affecting the bone marrow.
Unlike other types of anemia like iron deficiency anemia, this condition is not caused due to any kind of vitamin or mineral deficiency, which makes it a bit more difficult to diagnose and treat. Also, the symptoms of aplastic anemia are similar to those of other types of anemia, which further adds to the problem of diagnosing this condition.
Some of the causes of this condition are:
Poisoning and Toxicity
Exposure to toxic substances causes poisoning in the body, which may lead to this disorder. These include benzene, pesticide components, arsenic, and others.
Drugs and Medications
Certain drugs and medications have also been implicated as reasons causing this anemia. It may occur as a result of interaction with other drugs, or due to a direct adverse effect on the bone marrow. Such drugs include chloramphenicol, phenytoin, quinine, phenylbutazone, felbamate, and carbamazepine. However, the probability of these drugs alone causing the anemia is very low. For example, only 1 in 40,000 people undergoing treatment with chloramphenicol have a chance of developing it.
There a few diseases and disorders that adversely affect the bone marrow. For example, acute viral hepatitis. Other viral infections, like those caused by cytomegalovirus, parvovirus, Epstein-Barr virus, or HIV can also cause aplastic anemia. Certain autoimmune diseases, wherein white blood cells attack the bone marrow hampering the process of red blood cell production, like lupus, and rheumatoid arthritis could also lead to this disorder.
Chemotherapy and Radiation
One of the most dangerous probable causes is chemotherapy and radiation therapy; especially if it is being administered over a long period of time. In fact, blood and bones are one of the first to be affected by radiation, and they are affected quite gravely. The sudden onset of aplastic anemia is one of the radiation poisoning symptoms.
Bone Marrow Cancer
Bone marrow cancer is an important probable cause. Often resulting from radiation poisoning, bone marrow cancer severely affects the functioning of the bone marrow, leading to very low output of red blood cells. Besides radiation, bone marrow cancer may also result from metastasis of other types of cancer.
Certain other rare inherited disorders may also lead to this anemia; for example, Fanconi’s anemia, dyskeratosis congenita, or Shwachman-Diamond syndrome. In such cases, the treatment mostly involves repeated blood transfusions or, in severe cases, bone marrow transplant.
It was initially believed that aplastic anemia may run in families, and hence, be hereditary in nature. But this theory has not been validated yet. However, it is important to note that all the causes given above are suspected causes. Although a peripheral blood smear may help in diagnosing the condition, the treatment plan is difficult to chalk out. This is because, finding and pin-pointing the exact cause is not an easy task. In fact, many researchers still claim that the exact causes are unknown.