Do we know what causes aplastic anemia?

Most cases of acquired aplastic anemia have no known cause. In rare cases, the cause is exposure to certain chemicals such as benzene. Although many chemotherapy drugs and radiation treatment can damage the bone marrow, they don’t usually cause aplastic anemia. When a cause can be found, it is most often a drug or a viral infection. Environmental pollutants are another possible cause.

Doctors have tried to figure out how medicines, chemicals, and viruses can cause this disease. The most commonly accepted explanation is that these agents trigger an abnormal immune reaction in the body of some people. In this reaction, a type of immune cell called the T-cell (or T-lymphocyte) starts making too much of certain substances called cytokines. These cytokines are toxic to bone marrow cells and can cause them to die. Knowing that the anemia is caused by an abnormal immune reaction explains why the modern treatment of this disease with drugs that suppress the immune system has been very successful (see the section “How is aplastic anemia treated?”).