When the bone marrow cells (stem cells) that develop into mature blood cells and platelets are damaged or suppressed, the bone marrow can shut down. This bone marrow failure is called aplastic anemia. The bone marrow failure leads to too few red blood cells (anemia—see also Overview of Anemia Overview of Anemia Anemia is a condition in which the number of red blood cells is low. Red blood cells contain hemoglobin, a protein that enables them to carry oxygen from the lungs and deliver it to all parts... read more ), too few white blood cells ( leukopenia Overview of White Blood Cell Disorders White blood cells (leukocytes) are an important part of the body’s defense against infectious organisms and foreign substances ( the immune system). To defend the body adequately, a sufficient... read more ), and too few platelets ( thrombocytopenia Overview of Thrombocytopenia Thrombocytopenia is a low number of platelets (thrombocytes) in the blood, which increases the risk of bleeding. Thrombocytopenia occurs when the bone marrow makes too few platelets or when... read more ).
The term aplastic anemia is used to refer to anemia that occurs when production of most or all types of blood cells is suppressed. If production of only red blood cells is suppressed, the disorder is called pure red blood cell aplasia.
When the cause of aplastic anemia cannot be diagnosed (called idiopathic aplastic anemia), the cause is likely an autoimmune disorder Autoimmune Disorders An autoimmune disorder is a malfunction of the body's immune system that causes the body to attack its own tissues. What triggers autoimmune disorders is not known. Symptoms vary depending on... read more , in which the immune system suppresses bone marrow stem cells.
Other causes include
Infection with viruses such as parvovirus, Epstein Barr virus Infectious Mononucleosis Epstein-Barr virus causes a number of diseases, including infectious mononucleosis. The virus is spread through kissing. Symptoms vary, but the most common are extreme fatigue, fever, sore throat... read more , and cytomegalovirus Cytomegalovirus (CMV) Infection Cytomegalovirus infection is a common herpesvirus infection with a wide range of symptoms: from no symptoms to fever and fatigue (resembling infectious mononucleosis) to severe symptoms involving... read more
Toxins (such as benzene)
Chemotherapy drugs and other drugs (such as chloramphenicol)
Symptoms of Aplastic Anemia
Symptoms of aplastic anemia usually develop slowly over weeks to months.
The anemia causes fatigue, weakness, and paleness. The leukopenia causes increased susceptibility to infection. The thrombocytopenia causes easy bruising and bleeding.
Diagnosis of Aplastic Anemia
Bone marrow examination
Blood tests are done in people who have symptoms of anemia. When blood tests show that all blood cell numbers are reduced, a bone marrow examination is done.
Aplastic anemia is diagnosed when microscopic examination of a sample of bone marrow Bone Marrow Examination Red blood cells, most white blood cells, and platelets are produced in the bone marrow, the soft fatty tissue inside bone cavities. Sometimes a sample of bone marrow must be examined to determine... read more (bone marrow biopsy) reveals a sharp decrease in bone marrow cells.
Treatment of Aplastic Anemia
Stem cell transplantation
People with severe aplastic anemia may die unless immediately treated. Transfusions Overview of Blood Transfusion A blood transfusion is the transfer of blood or a blood component from one healthy person (a donor) to a sick person (a recipient). Transfusions are given to increase the blood's ability to... read more of red blood cells, platelets, and substances called growth factors may temporarily increase the numbers of red blood cells, white blood cells, and platelets.
Stem cell transplantation Stem Cell Transplantation Stem cell transplantation is the removal of stem cells (undifferentiated cells) from a healthy person and their injection into someone who has a serious blood disorder. (See also Overview of... read more is the usual treatment in aplastic anemia because it may cure the disease, especially in younger people who have a matched stem cell donor. If transplantation is not possible, people are given antithymocyte globulin and cyclosporine to suppress the immune system and allow the bone marrow stem cells to regenerate.