What is Thalassemia?
Thalassemia is an inherited blood disorder in which parents pass the genes for disorder on to their children. It reduces reproduction of red blood cells in human body. In thalassemia patient, the genes that control globin production are mutated or deleted. As a result, formation of the corresponding globin chains is trimmed down and an abnormal hemoglobin ratio is enhanced. This abnormal ratio leads to a decreased synthesis of hemoglobin and expression of thalassemia. Professor Dr. Mamun Ahmed from the Department of Biochemistry and Molecular Biology, Dhaka University explained, “If one among 23 pairs of chromosomes of one’s body is affected by Alpha or Beta chain mutation, one may become victim of Thalassemia. If both the chromosomes of a pair are affected, chance is 25 percent that the person will be victim of this lethal disease.” Thalassemia causes mutation in the DNA of cells that make hemoglobin, the substance in the red blood cells that carries oxygen throughout the body. The mutations thus disrupt the normal production of hemoglobin and cause low hemoglobin levels and a high rate of red blood cell destruction, causing anemia. Due to anemia, the blood does not have enough red blood cells to carry oxygen to the tissues, leaving one fatigued. Epidemiology
Generally, thalassemia is prevalent in the people living in humid climate zones where malaria was endemic in the past or still exists. Since thalassemia acts as an antidote to malaria because of the blood cells' easy degradation, it got epidemic in those regions. Thalassemia was first detected among Mediterranean inhabitants. In fact, this geographical association is responsible for its naming: Thalassa is Greek for the sea, Haema is Greek for blood. In Europe, the highest concentrations of the disease are found in Greece, coastal regions of Turkey, Southern Italy and the lower Po valley. The major Mediterranean islands (except the Balearics) such as Sicily, Sardinia, Malta, Corsica, Cyprus, and Crete are heavily affected in particular. High rate of thalassemia is also seen among other Mediterranean people, as well as those in the vicinity of the Mediterranean, including people from West Asia and North Africa. Far from the Mediterranean, South Asians are also affected. The Maldives has the highest incidence of Thalassemia in the world with a carrier rate of 18% of the population. Likewise, lots of people from Bangladesh, China, India, Malaysia and Pakistan are also believed to be thalassemia carriers. Descendants of people from Latin America and Mediterranean countries are other notable thalassemia carriers. Furthermore, a very low prevalence has been reported from people in Northern Europe (0.1%) and Africa (0.9%), with those in North Africa having the highest frequency. Types of Thalassemia
Normal hemoglobin, known as hemoglobin A, has four protein chains – two Alpha globins and two Beta globins. The two major types of thalassemia, Alpha and Beta, are named after defects in these protein chains. Both Alpha and Beta thalassemias include the following two forms: * Thalassemia major
* Thalassemia minor
Thalassemia major occurs as a result of inheritance of defective gene from both parents, while thalassemia minor occurs if the defective gene is received from only one parent. Persons with the minor form of the disorder are carriers of the disease and usually do not have symptoms. Alpha Thalassemia
Four genes (two from each of the parents) are involved in making the Alpha hemoglobin chain. Alpha thalassemia trait occurs if one or two of the four genes are deleted or mutated. Four possible cases of Alpha thalassemia can be observed. * One mutated gene: There will be no signs or symptoms of thalassemia. However, there is always a risk of passing this disease to the predecessors. * Two mutated genes: It may cause mild anemia. This condition is called Alpha thalassemia minor. * Three mutated genes: Signs and symptoms will be...
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