Thalassemia overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [2] Shyam Patel [3]
Overview
Thalassemia (British spelling, "thalassaemia") is an inherited autosomal recessive blood disease. In thalassemia, the genetic defect results in reduced rate of synthesis of one of the globin chains that make up hemoglobin. Reduced synthesis of one of the globin chains causes the formation of abnormal hemoglobin molecules, and this in turn causes the anemia which is the characteristic presenting symptom of the thalassemias.
Thalassemia is a quantitative problem of too few globins synthesized, whereas sickle-cell disease (a hemoglobinopathy) is a qualitative problem of synthesis of a non-functioning globin. Thalassemias usually result in under production of normal globin proteins, often through mutations in regulatory genes. Hemoglobinopathies imply structural abnormalities in the globin proteins themselves [1]. The two conditions may overlap, however, since some conditions which cause abnormalities in globin proteins (hemoglobinopathy) also affect their production (thalassemia). Thus, some thalassemias are hemoglobinopathies, but most are not. Either or both of these conditions may cause anemia.
Historical Perspective
Our knowledge about the origins of thalassemia date back to more than 6000 years ago. At that time, persons of Mediterranean descent began their migrations to other regions of the world, carrying gene variants that eventually gave rise to thalassemias. The expansion of empires led to further propagation of the defective globin genes throughout the world. It was soon noted that persons with thalassemia were relatively resistant to malaria, and further molecular studies were done to identify the underlying pathophysiology of thalassemias. The initial treatment approach to thalassemia was supportive care, especially red blood cell transfusions. In the recent years, bone marrow transplant and gene therapy have been exploited as possible treatments to treat thalassemias. These treatment strategies are still being explored.