Thalassemia is a disorder affecting the blood, in which the body of an individual manufactures an abnormal form of haemoglobin. Haemoglobin is present in your red blood cells and is the main carrier of oxygen to various parts of your body. It is a disorder which is inherited and is passed down through families. The abnormal haemoglobin formed is unable to bind with oxygen and there is an excessive destruction of the red blood cells which leads to anemia.
Hemoglobin is made up of two types of proteins namely the Alpha globin and Beta globin. Specific genes in your body code these proteins and help in manufacturing them. Thalassemia occurs when gene defects affect the production of Alpha globin chains or the Beta globin chains. Alpha thalassemia and Beta Thalassemia can be divided into thalassemia major and thalassemia minor. The defective genes coding for the two types of globin chains, run in families. Thus if you inherit defective genes from both your parents you will suffer form thalassemia major and if you inherit a defective gene form only one parent, you will be a carrier of the disease and are relatively asymptomatic. This is called as thalassemia minor.
Alpha thalassemia occurs commonly among people from the Middle East, India, China, southeast Asia and those of African descent.
Alpha globin is coded by four genes. These genes are present on chromosome 16. Two genes are present on each strand of chromosome 16. Individuals may have one alpha globin gene abnormal, and thus be a silent carrier or alpha thalassemia. As one of the four alpha globin genes is missing there is a minimal lack of alpha globin protein and the individual does not suffer from anaemia. Infact most people are unaware that they are carriers of alpha thalassemia. The diagnosis is established by special DNA testing. It can also be diagnosed when an apparently normal individual has a child who has alpha thalassemia minor or haemoglobin H disease.
An individual having two abnormal alpha globin genes is said to have alpha thalassemia trait. The two defective genes can be either of the four, two from the same chromosome which is known as cis position or one on each strand of a pair which is known as trans position. The alpha globin protein chains are further decreased in amount. Such individuals present which anaemia.
Most doctors commonly diagnose alpha thalassemia trait as iron deficiency anaemia and as a routine prescribe iron supplements. However this anaemia is not going to respond to iron supplementation. Patients suffering from alpha thalassemia trait may be asymptomatic. On routine blood examination they found to have smaller red blood cells and a mild anaemia.
Alpha thalassemia traits can combine in various ways to produce blood disorders which can range in severity from mild to severe as regards their effects. For example both the parents carry alpha thalassemia trait in which the two abnormal genes of each parent are on the opposite chromosomes their children will inherit alpha thalassemia trait.
If both the parents carry alpha thalassemia trait with the two abnormal genes on the same chromosome there is a 25% chance with each pregnancy that their child will inherit hydrops fetalis or alpha thalassemia major in which all of the four alpha globin genes are abnormal. Such children are not able to survive and usually die shortly after birth. In case they do survive these children need lifelong blood transfusions and close medical supervision.
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