30-08-2011, 09:49 AM
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Introduction:
Most of our physical characteristics are inherited through the genes we take from our parents; for example, the shape of our nose, the color of our skin and eyes. We also inherit our hemoglobin type from our parents, through the genes. Hemoglobin is the substance in the blood which gives it its red color. It carries the oxygen we breathe to all our body parts; thus is vital for life. Thalassemia is an inherited blood disorder in which the body is unable to make adequate hemoglobin. Hemoglobin is present in the red cells and is made from proteins. These proteins consist of alpha(α) and beta(β) chains. Normally 2 alpha and 2 beta chains are essential to form hemoglobin. Imbalances in these chains results in reduced red cell survival. The amount of beta and alpha chains a person makes is controlled by the hemoglobin gene they inherit from their parents. Normally red cells survive for 120 days but in Thalassemia red cell survival is reduced.
Thalassemia can be categorized into three classes depending on clinical expression: thalassemia major (TMA), a severe disorder leading to transfusion dependence; thalassemia intermedia (TI), relatively milder involving less transfusion dependence; and thalassemia minor (TMI), where individuals carry the heterozygous mutation but do not exhibit any of the symptoms and usually do not require blood transfusion.1 If both parents have TMI there exists a 25% probability in each pregnancy that their child will have TMA, a 50% probability that the child will have TMI and a 25% probability that a child will have neither mutation . The classification of TMA or TI also depends on the age of onset of symptoms, degree of anemia, age when first transfused, transfusion requirements per year, and growth or enlargement of the spleen.
