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Alpha-thalassemia (a-thalassemia) is a form of thalassemia involving the genes HBA1 [1] and HBA2 [2].
It is most commonly inherited in a Mendelian recessive fashion. It is also connected to the deletion of the 16p chromosome.
It can also be acquired.[3]
a thalassemias result in decreased alpha-globin production, therefore fewer alpha-globin chains are produced, resulting in an excess of ß chains in adults and excess ? chains in newborns. The excess ß chains form unstable tetramers (called Hemoglobin H or HbH of 4 beta chains) which have abnormal oxygen dissociation curves.
There are two genetic loci for a globin, and thus four alleles. Two alleles are maternal in origin and two alleles are paternal in origin. The severity of the a thalassemias is correlated with the number of affected a globin allele: the greater the number of affected loci, the more severe will be the manifestations of the disease.
When noting the genotype, a “-” indicates an absence of function, and a “a” indications a functional alpha chain. (In contrast to the “ßo” and “ß+” notation used in beta-thalassemia, in alpha-thalassemia a distinction between absent and reduced function is not usually noted.)
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