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Beta thalassemias ( β thalassemias) are a group of inherited blood disorders. They are forms of thalassemia caused by reduced or absent synthesis of the beta chains of hemoglobin that result in variable outcomes ranging from severe anemia to clinically asymptomatic individuals. Global annual incidence is estimated at one in 100,000. [4]
In this form, some hemoglobin A is produced; β thalassemia minor is caused by a β/β o or β/β + genotype. Only one of the two β globin alleles contains a mutation, so β chain production is not terribly compromised and patients may be relatively asymptomatic. Beta thalassemia most often occurs in people of Mediterranean origin.
There are two main groups: abnormal structural hemoglobin variants caused by mutations in the hemoglobin genes, and the thalassemias, which are caused by an underproduction of otherwise normal hemoglobin molecules. The main structural hemoglobin variants are HbS, HbE and HbC. The main types of thalassemia are alpha-thalassemia and beta thalassemia.
Beta thalassemia minor results in a mild microcytic anemia that is often asymptomatic or may cause fatigue and or pale skin. Beta thalassemia major occurs when a person inherits two abnormal alleles. This can be either two β+ alleles, two β0 alleles, or one of each. Beta thalassemia major is a severe medical condition.
In beta-thalassemia major, hemoglobin A is decreased (or in some cases absent) and hemoglobin F is markedly elevated; A2 levels are variable. [3] : 461–2 In hemoglobin H disease , a form of alpha-thalassemia , an abnormal band of hemoglobin H can be detected, and sometimes a band of Hemoglobin Barts ; but in the milder alpha-thalassemia trait ...
Beta-thalassemia. Beta-thalassemia (β-thalassemia) is an inherited mutation of the β-globulin gene which causes the reduced synthesis of the β-globin chain of hemoglobin. The majority of the mutations are point mutations that affect translation, transcriptional control, and splicing of the hemoglobin β gene and gene product.
Hemoglobin E ( HbE) is an abnormal hemoglobin with a single point mutation in the β chain. At position 26 there is a change in the amino acid, from glutamic acid to lysine (E26K). Hemoglobin E is very common among people of Southeast Asian, Northeast Indian, Sri Lankan and Bangladeshi descent. [1] [2]
Mechanism. Delta-beta thalassemia is autosomal recessive disorder, [1] which means both parents are affected and two copies of the gene must be present. [5] A carrier gets a normal gene to produce hemoglobin A, from one parent and the other parent supplies a gene which makes no hemoglobin A. [6] Delta-beta thalassemia is considered rare.