Beta Thalassemia

Excerpt

Thalassemias are a common cause of hypochromic microcytic anemia which arises from the reduced or absent synthesis of the globin chain of hemoglobin. Thalassemias are a quantitative defect of hemoglobin synthesis. This is in contrast with hemoglobinopathies, such as sickle cell disease, which are structural or qualitative defects of hemoglobin. Beta-thalassemia refers to an inherited mutation of the beta-globin gene, causing a reduced beta-globin chain of hemoglobin. The highest prevalence of beta-thalassemia mutations is in people of Mediterranean, Middle Eastern, and Asian descent. Over 200 different thalassemia-causing mutations have been identified in the beta-globin gene, leading to the disease's wide genotypic and phenotypic variability. The three classifications of beta-thalassemia are defined by their clinical and laboratory findings. Beta-thalassemia minor, also called carrier or trait, is the heterozygous state that is usually asymptomatic with mild anemia. Homozygosity or compound heterozygosity for beta-thalassemia mutations cause a more severe spectrum of anemias called beta-thalassemia intermedia and beta-thalassemia major. These two are distinguished clinically by transfusion dependence. Beta-thalassemia major requires routine transfusions, and intermedia does not.

Laboratory findings suggestive of thalassemia include microcytic hypochromic anemia. There may be significant anisopoikilocytosis (variation of size and shape) in cases of beta-thalassemia major on peripheral smear. Exclusion of iron deficiency and hemoglobin electrophoresis or high-performance liquid chromatography are often required for diagnosis. Treatment, if required, is primarily with blood transfusion, depending on the degree of anemia. Complications of beta-thalassemia include iron overload and bone-deforming marrow expansion with extramedullary hematopoiesis.