Thalassemia

Thalassemia is a group of diseases with hereditary disruption of globin protein synthesis, which is part of hemoglobin. Globin consists of several chains of amino acids, namely from 2 a- and 2-c-chains. With thalassemia, a synthesis of any of these chains may occur. The street with this disease develops severe or insignificant anemia, and the iron content in the serum remains normal or increases.

Thalassemia was first described in 1925 by American pediatricians. They observed 5 children who showed signs of severe anemia, a significant increase in the spleen and liver, and bone changes. After the publication of their report, the work of Italian authors appeared, describing a similar, but substantially easier form of the disease, in which people survived to adulthood and had children. The term "thalassemia" was proposed in 1936. For the first time the idea that thalassemia is the result of a breakdown in the synthesis of globin protein chains was expressed independently by several scientists. Thalassemia, in which the synthesis of the β-chain of the globin is broken, is called β-thalassemia. With α-thalassemia, synthesis of the α-chain of the protein is disrupted. More common is β-thalassemia.

In thalassemia, one of the chains of the globin is formed in small amounts or does not form at all. Normally, the formation of chains of the protein globin is balanced. The number of α- and β-chains is the same, and there are no free globin chains. The broken synthesis of one of them leads to a disbalance. The chain, which is produced in excess, is compacted and deposited in erythrocaryocytes( red bone marrow cells, which are precursors of red blood cells).This is associated with most of the manifestations of thalassemia. The absence of an α-chain in the fetus leads to the development of dropsy and intrauterine death.

In the development of thalassemia, the main emphasis is placed on the excessive amount of any globin chain. Thus, in β-thalassemia, in connection with the breakdown of the synthesis of the β-chain, there are many free α-chains. If these excess chains are not included in the fetal hemoglobin, they become denser and precipitate. Excess formation of the α-chain is the main cause of ineffective formation of mature erythrocytes in β-thalassemia. Erythrocaryocytes( precursors of erythrocytes) die in the bone marrow. The death of bone marrow erythrocaryocytes leads to severe anemia. In this case, in the spleen and in the liver, foci of additional red hemopoiesis may appear. Excessive hematopoiesis in the bones leads to their deformation, a pronounced oxygen deficiency( hypoxia) - to disrupt the development of the child. Between the depth of anemia and the excess of the α-chain with β-thalassemia, a clear relationship is evident. With α-thalassemia, in the absence of α-chain formation, and in connection with this hemoglobin A( hemoglobin of an adult human) and F( hemoglobin of the fetus), fetal hydrops develop which leads to death. Excess of β-chains in thalassemia is able to form hemoglobin, consisting of 4β-chains - hemoglobin H. Cells containing hemoglobin H are very easily removed from the blood by the spleen, in which they are destroyed. Anemia in the formation of hemoglobin H is due to both the destruction of erythrocytes in the spleen, and the violation of the formation of globin protein.