Beta-thalassemia overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Maryam Hadipour, M.D.[2]
Overview
Historical Perspective
The Thalassemia term was invented by an hematologist, Dr. Thomas Cooley, in 1925. It has a Greek origin and consists of Thalassa and Emia which mean sea and blood, respectively. The diagnostic certainty was ultimately established with hemoglobin electrophoresis in the 20th century.
Classification
Beta-Thalassemia is classified based on the severity and the type of responsible mutation. It mainly has 3 types: β thalassemia minor, β thalassemia major, Thalassemia intermedia. There are less common types such as E/Beta-thalassemia, autosomal dominant Beta-thalassemia and atypical Beta-Thalassemia.
Pathophysiology
Beta-Thalassemia is an inherited disorder in hemoglobulin production due to a variety of genetic mutations in the gene responsible for Beta-globin production (HBB gene, on chromosome 11). The effects of beta-thalassemia on red blood cell morphology and function are significantly detrimental. Beta-Thalassemia contributes to abnormal hemoglobin and red blood cells (RBCs) that have impaired function in efficient oxygen delivery to different body tissues, which is called the state of anemia. As mutated genes are passed down, the shortage of functional red blood cells begins affecting the body from early infancy, and the lifelong persistence of insufficiency in beta-globin production results in chronic anemia. Hepatosplenomegaly, delayed developmental milestones, jaundice, bone problems, and different infections might happen in early infancy.
Differentiating Beta-thalassemia from other Diseases
Beta-thalassemia may have similar features of other conditions such as iron deficiency anemia, sideroblastic anemia, Alpha-thalassemia, other hemolytic anemia and other hemoglobinopathies including sickle cell anemia. To differentiate these conditions, history and physical examination, electrophoresis of hemoglobin, DNA analysis and iron level assessments would be useful.
Epidemiology and Demographics
The prevalence of beta-thalassemia carrier is 1.5% of the world population which is mainly in regions with a historical association with malaria, including the Mediterranean, Middle East, Central Asia, Indian subcontinent, and parts of Southeast Asia and Africa. The incidence of beta-thalassemia is 42,000 per year. It affects both males and females in a similar demographic manner.
Risk Factors
In General, Positive family history and specific ethnicities are the major risk factors for beta-thalassemia. On the other hand, Lack of awareness and education about the screening for beta-thalassemia, limited resources for screening programs and the consanguineous marriages are contributing factors for increasing the risk of beta-thalassemia.
Natural History, Complications and Prognosis
Without regular blood transfusions, affected individuals by major beta-thalassemia typically develop severe anemia and related complications early in life, while beta-thalassemia intermedia patients would have a variable clinical course, complications, and prognosis. beta-thalassemia minor subjects would not have significant symptoms, while in some cases might have an increased risk for iron deficiency anemia. Iron overload complications happen in transfusion-dependent thalassemia.