Aplastic anemia is a rare, potentially fatal disease in which the bone marrow doesn't make enough blood cells. The bone marrow is the central portion of the bones that is responsible for making:
Red blood cells, which carry oxygen
White blood cells, which fight infection
Platelets, which help blood to clot
The bone marrow releases the cells and platelets into the blood stream.
A complete blood count (CBC) is a blood test that measures the number of red cells, white cells and platelets circulating in the blood stream. People with aplastic anemia have low levels of all three types of blood cells that are normally manufactured in the bone marrow.
Aplastic anemia is a problem with cells in the bone marrow called stem cells. Stem cells are the basic "mother cells" that develop into the three types of blood cells. In aplastic anemia, something either destroys the stem cells or drastically changes the environment of the bone marrow so that the stem cells can't develop properly. Several factors can cause this problem, including:
Exposure to radiation (radiation sickness)
Environmental toxins (insecticides, benzene, nitrogen mustards)
Many different medications, including chloramphenicol (Chloromycetin), phenylbutazone (Butazolidin), sulfonamides (Gantanol and others), anticonvulsants, cimetidine (Tagamet) and others
Certain viral infections, including viral hepatitis B, parvovirus B19, HIV and infectious mononucleosis (Epstein-Barr viral infection)
Autoimmune disease, where the body inappropriately attacks its own blood stem cells
Some people are more likely to develop aplastic anemia because of their genetic (inherited) makeup. Fanconi's anemia is an inherited condition that causes aplastic anemia and also physical abnormalities. Some women develop a mild form of aplastic anemia during pregnancy, but it tends to disappear after delivery. In 50% to 65% of patients with aplastic anemia, the cause of the illness is not clear.
Aplastic anemia strikes two to six of every 1 million people each year in the United States and Europe. The disease affects one of every 25,000 to 40,000 of those who are treated with the medication chloramphenicol (now rarely used in the United States), but it is much rarer in people treated with other drugs.