Aplastic Anemia

By: Ragujo

Under normal circumstances, our bone marrow pumps out up to one trillion (Gordon Lewis & Marley, 2002) new blood cells each day! It functions like a very efficient factory, housing tens of thousands (Gordon,Lewis & Marley, 2002) of amazing machines (pluripotent hematopoetic stem cells) that can churn out three of the most highly demanded consumer goods (red blood cells, white blood cells, and platelets).  Different chemicals in the body function as foremen, telling the machines what type of cell to produce.  Occasionally a person’s bone marrow will fail and the factory slows production dramatically.  The products are still made well, but the factory just can’t keep up with demand.  This type of marrow failure is called aplastic anemia and is a very rare and serious condition.

Reducing numbers of all three blood cell types can have a profoundly negative impact on one’s quality of life.  Our red blood is responsible for carrying oxygen throughout the body, and when those counts are low (anemia) people commonly experience dizziness, fatigue, shortness of breath, irregular heartbeats and pallor.  Our white blood cells are strong players in our immune system, keeping us safe from viral and bacterial infections.  When we lack white blood cells (neutropenia) then our risk of infection increases immensely, and any infection requires medical intervention.  Platelets are part of the clotting process and when they are reduced (thrombocytopenia) an individual is at risk for heavy bleeding and may bruise easily.  Nosebleeds, bleeding gums and petichiae (pinpoint red spots on the skin) are common signs of low platelet counts (Aplastic Anemia, 2014b). If untreated, these conditions will lead to death. 

In most cases of aplastic anemia the first course of treatment is to alleviate symptoms of anemia and thrombocytopenia by transfusing platelets and red blood.  Hand washing, antibiotics and avoiding densely populated areas can help keep a neutropenic individual avoid infection. These will help meliorate an immediate situation but long-term recovery is often achieved through a combination of immunosupressive therapies and/or bone marrow transplant.  Because aplastic anemia is thought to be caused by abnormal expression of T cells that attack the hematopeitic stem cells, the immunotherapies used interfere with the activity of T cells (Bacigulpo, 2007).  T cells are a type of white blood cell that are trained to  attack foreign cells in order to keep us healthy, and should know to leave our cells alone. Stopping the activity of  abnormal T cells allows bone marrow to rebuild its supply of stem cells and then blood cells. Antithymocyte globulin is the most successful immune therapy and when used with cyclosporine will improve blood counts in 7 out of 10 cases (Aplastic Anemia, 2015). Bone marrow transplantation will often be performed before immunosuppressive therapy if a matched sibling donor is available.  If immunotherapy does not improve counts, and no sibling match is available, then an unrelated donor will be sought. Survival rates after bone marrow transplants are much higher when the donor is a relative, but success rates for unrelated donor transplants are improving.  Both treatments show higher success rates in younger patients and when started soon after diagnosis (Bacigulpo, 2007).

Aplastic anemia is very rare, affecting roughly 2.0 individuals/million population in Europe and around 4.0 individuals/million population in Asian countries (Young & Kaufman, 2008).  Because the incidence rate for people of Asian descent living in the U.S. or Europe is comparable to the European incidence rate, the increased number of cases in Asia suggests that environmental factors could be more influential than genetic factors in disease development (Young & Kaufman, 2008).  Toxins, such as solvents and pesticides, as well as medical drugs have been linked to several cases of aplastic anemia.  In other cases, bone marrow failure is thought to have been caused by infection – infectious mononucleosis, hepatitis, HIV and leukemia are conditions that can sometimes lead to aplastic anemia.  Overall, however, 75% of aplastic anemia cases are idiopathic, which means the cause is unknown (Aplastic Anemia, 2014a; Young & Kaufman, 2008). Because the underlying cause of marrow failure is typically unknown, there is no sure way to prevent it.  Minimizing exposure to harsh chemicals and infectious diseases can minimize risk of developing aplastic anemia.

References

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http://www.aamds.org/about/aplastic-anemia/causes

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              symptoms. Retrieved from:

              http://www.aamds.org/about/aplastic-anemia/symptoms

Aplastic Anemia & MDS International Foundation. (2015). Immunosuppressive drug

therapy. Retrieved from:

              http://www.aamds.org/about/aplastic-              anemia/treatment/immunosuppressives

Bacigulpo, A. (2007) . Aplastic anemia: pathogenesis and treatment. ASH Education             Book, 1, 23-28.

 DOI: 10.1182/asheducation-2007.1.23

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Johns Hopkins Sydney Kimmel Comprehensive Cancer Center.  (n.d). Aplastic anemia.

Retrieved from:

http://www.hopkinsmedicine.org/kimmel_cancer_center/types_cancer/aplastic_anemia.html

Young, N. & Kaufman, D.  (2008).  The epidemiology of acquired aplastic anemia.

Hematologica, 93, 489-492. DOI: 10.3324/haematol.12855