What is thalassemia? causes, symptoms, clinical features?
Thalassemia Thalassemias are inherited disorders caused by mutations in globin genes that decrease the synthesis of α- or β-globin. Decreased synthesis of one globin results not only in a deficiency of Hb but also in red cell damage that is caused by precipitates formed from excess unpaired "normal" globin chains. The mutations that cause thalassemia are particularly common in Mediterranean, African, and Asian regions in which malaria is endemic. As with HbS, it is hypothesized that globin mutations associated with thalassemia protect against falciparum malaria. Pathogenesis A diverse collection of α-globin and β-globin mutations underlies the thalassemias, which are autosomal codominant conditions. Adult hemoglobin (HbA) is composed of two α chains and two β chains. α chains are encoded by two α-globin genes on chromosome 16. β chains are encoded by a single β-globin gene on chromosome 11. Clinical features vary widely depending on the combination of mutated alleles inherite...