β-Thalassemias are extremely heterogeneous at the molecular level. More than 200 disease-causing mutations have been identified. The majority of mutations are single nucleotide substitutions. Rarely, β-thalassemia results from gross gene deletion. The degree of globin chain imbalance is determined by the nature of the mutation of the β-gene. β0 refers to the complete absence of production of β-globin on the affected allele. β+ refers to alleles with some residual production of β-globin (around 10%). In β++, the reduction in β-globin production is very mild. The broad spectrum of β-thalassemia alleles can produce a wide spectrum of different β-thalassemia phenotypes. In this chapter, we review the molecular basis of the marked heterogeneity of the thalassemia syndromes or in other words the genotype-phenotype relationship in β-thalassemia.
Part of the book: Epidemiology of Communicable and Non-Communicable Diseases