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Aplastic Anemia

by Alan E. Lichtin, MD

When the bone marrow cells that develop into mature blood cells and platelets (stem cells) are damaged or suppressed, the bone marrow can shut down. This bone marrow failure is called aplastic anemia. A common cause of aplastic anemia is an autoimmune disorder, in which the immune system suppresses bone marrow stem cells. Other causes include infection with parvovirus, radiation exposure, toxins (such as benzene), chemotherapy drugs, and other drugs (such as chloramphenicol).

The bone marrow failure leads to too few red blood cells (anemia), too few white blood cells (leukopenia), and too few platelets (thrombocytopenia). The anemia causes fatigue, weakness, and paleness. The leukopenia causes increased susceptibility to infection. The thrombocytopenia causes easy bruising and bleeding. In some people, only red blood cell production is affected (resulting in a condition called pure red blood cell aplasia). When parvovirus infection is the cause, only red blood cell production is likely to be affected.

Aplastic anemia is diagnosed when microscopic examination of a sample of bone marrow (bone marrow biopsy) reveals a sharp decrease in the number of stem cells and in the maturation of blood cells.

People with severe aplastic anemia quickly die unless immediately treated. Transfusions of red blood cells, platelets, and substances called growth factors may temporarily increase the numbers of red blood cells, white blood cells, and platelets. Initial treatment of aplastic anemia is with antithymocyte globulin, a drug that suppresses certain cells in the immune system. People who do not respond to antithymocyte globulin may be given cyclosporine, an immunosuppressant. Stem cell or bone marrow transplantation can sometimes cure aplastic anemia. People without a suitable stem cell donor often respond to treatment with corticosteroids and drugs that suppress the immune system.

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