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Alpha-thalassemia (α-thalassemia, α-thalassaemia) is an inherited blood disorder and a form of thalassemia. Thalassemias are a group of inherited blood conditions which result in the impaired production of hemoglobin , the molecule that carries oxygen in the blood. [ 4 ]
If hemoglobin Barts is detected on a newborn screen, the patient is usually referred for further evaluation since detection of hemoglobin Barts can indicate either one alpha globin gene deletion, making the baby a silent alpha thalassemia carrier, two alpha globin gene deletions (alpha thalassemia), or hemoglobin H disease (three alpha globin ...
Thalassemia subtypes of clinical significance are alpha thalassemia and beta thalassemia. A third subtype, delta thalassemia, affects production of HBA2 and is generally asymptomatic. [26] The severity of alpha thalassemia depends on how many of the four genes that code for alpha globin are faulty.
Alpha thalassemia is caused by deficient production of the alpha globin component of hemoglobin, while beta thalassemia is a deficiency in the beta globin component. [7] The severity of alpha and beta thalassemia depends on how many of the four genes for alpha globin or two genes for beta globin are faulty. [2]
Alpha-thalassemia (α-thalassemia) is defined by a lack of α-globin chain production in hemoglobin, and those who carry a mutation impacting the α-globin chain on only one chromosome are considered to have a “silent” α-thalassemia whereas, if the mutation is on both then it is considered an α-thalassemia trait.
It is the most common nondeletional alpha-thalassemia mutation associated with hemoglobin H disease. [1] The quantity of hemoglobin in the cells is low because the messenger RNA is unstable and some is degraded prior to protein synthesis. Another reason is that the Constant Spring alpha chain protein is itself unstable.
Thalassemia results in nontransferrin-bound iron being available in blood as all the transferrin becomes fully saturated. This free iron is toxic to the body since it catalyzes reactions that generate free hydroxyl radicals. [6] These radicals may induce lipid peroxidation of organelles like lysosomes, mitochondria, and sarcoplasmic membranes.
Alpha thalassemia patients have partial or complete defects in alpha globin production, leading to a relative abundance of beta globin chains in the cell. These excess beta globin chains aggregate to form HbH , which has decreased solubility and precipitates in the red blood cell cytoplasm . [ 10 ]