thelesemia |
The thalassemias are a diverse group of genetic blood diseases characterized by absent or decreased production of normal hemoglobin, resulting in a microcytic anemia of varying degree. The thalassemias have a distribution concomitant with areas were malaria is common. People with Thalassemia Minor are able to fight malaria better than those who do not have it - therefore, in parts of the world where malaria existed Thalassemia Minor increased. This was of great value in the past since malaria was rampant and deadly. However, malaria is no longer a problem in many areas of the world, and Thalassemia Minor has no advantage to people in these areas. The alpha thalassemias are concentrated in Southeast Asia, Malaysia and southern China. The beta thalassemias are seen primarily in the Mediterranean Sea area, Africa and Southeast Asia. Due to global migration patterns, there has been an increase in the incidence of thalassemia in North America in the last ten years.
In the thalassemia patient, a mutation or deletion of the genes that control globin production occurs. This leads to a decreased production of the corresponding globin chains and an abnormal hemoglobin ratio. This abnormal ratio leads to decreased synthesis of hemoglobin and the expression of thalassemia. The globin that is produced in normal amounts winds up in excess and forms red cell aggregates or inclusions. These aggregates become oxidized and damage the cell membrane, leading to hemolysis, ineffective erythropoiesis, or both. The quantity and properties of these globin chain aggregates determine the characteristics and severity of the thalassemia.