Aplastic anemia is a serious disorder in which an inadequate number of red blood cells, white blood cells, and platelets in the blood (pancytopenia) result from bone marrow failure (aplasia), which is caused by injury to or suppression of the blood's stem cell. When the bone marrow fails to produce stem cells, the lack of red blood cells results in anemia. The lack of white blood cells results in infection, and the lack of platelets results in bleeding manifestations.
Aplastic anemia can be inherited or acquired. Primary or idiopathic aplastic anemia has no known cause, is difficult to treat, and accounts for about half of all cases.
Primary aplastic anemia may also occur during pregnancy but resolves following delivery.
Secondary aplastic anemia includes those disorders for which causes have been discovered.
Anticancer treatments (radiation or chemotherapy), viral infections, and certain drugs can interfere with the bone marrow's ability to produce cells.
In these cases, once the cause is removed, the bone marrow usually recovers and resumes normal production of cells.
A more persistent form of aplastic anemia is caused by long-term exposure to benzene fumes (a constituent of gasoline), exposure to insecticides, or exposure to a moderate to high dose of nuclear radiation (from radioactive fallout or nuclear explosions).
Aplastic anemia is most common around the age of 30.
- History: Symptoms usually develop gradually and include fatigue, lethargy, and shortness of breath due to a low level of red blood cells. As the number of white blood cells decrease, the individual may report feeling ill or feverish or developing frequent infections. A reduction in platelets may lead to easy bruising, oozing around the gums, and nosebleeds.
- Physical exam may be completely normal. In other cases, the exam may reveal paleness of the skin, nailbeds, and mucous membranes. There may be evidence of bruising, bleeding, or infection. Heart rate may be abnormally fast.
- Tests: A complete blood count (CBC) will usually show reduced numbers of red cells, white cells, and platelets, the hallmark of this disorder. A reticulocyte (immature blood cell) count will be very low, showing no attempt of the bone marrow to respond to the anemia.
A bone marrow analysis should include an aspirate (sample of cells from the bone marrow removed by suction through a needle) and a biopsy (a small core of bone with marrow inside) for microscopic examination. In aplastic anemia, the marrow shows an absence of blood forming cells (hypocellular).
Treatment varies according to the type of aplastic anemia.
If a chemical agent has caused the problem, removing it sometimes leads to a full recovery in individuals of all ages.
Generally, mild cases of aplastic anemia are treated with blood transfusions until the bone marrow resumes normal function.
During this period the individual is put on antibiotics to decrease the risk of infection.
In severe cases, a bone marrow transplant can be done if a suitable donor is available.
The donor must be someone whose tissue type is a genetically close match to the individual (usually a brother or sister).
This technique essentially repopulates the bone marrow with new, active stem cells.
Adults over 50 or other individuals who do not have compatible donors are usually treated with antithymocyte globulin (an immune system inhibitor) in conjunction with transfusion, antibiotics, and steroids.
The success of this treatment has helped confirm the notion that the immune system plays a role in most cases of aplastic anemia.
This therapy is occasionally combined with other immunosuppressive drugs (cyclosporine).
Injections of EPO (erythropoietin) and gCSF (granulocyte colony stimulating factor) are also used in the hopes of raising the white blood cell (hemoglobin neutrophil) count and decreasing anemia and infections.
Complications of aplastic anemia include increased risk of infection and hemorrhage. Untreated, it can rapidly become fatal. In pregnancy, aplastic anemia can result in premature birth and increase the risk for mother and/or infant mortality (death).
Without treatment, individuals with severe aplastic anemia will live an average of only three months following diagnosis. Most treatment is 50 to 80% successful. Chemically caused aplastic anemia usually resolves quickly when the exposure to the chemical is eliminated. Individuals who receive antithymocyte globulin typically show improvement in one to three months, with blood counts high enough that they will not require transfusions in the future. Bone marrow transplants are usually quite successful in older individuals (with sibling donors) and in children who have never had blood transfusions.
The symptoms of aplastic anemia, particularly pancytopenia, can be indicative of other disorders such as leukemia, lupus, AIDS, tuberculosis, and myelophthisic anemia.
Hematologist, rheumatologist and medical toxicologist.