Thalassaemia (part 1)

Abstract

The thalassaemias are a group of inherited blood disorders characterised by decreased or absent globin chain synthesis. Classification of thalassaemia is based on the type of globin chain that is deficient. There are four globin chain subtypes, viz. α, β, γ and δ; deficiencies of these are designated as α-, β-, γ- or δ-thalassaemia, respectively. As genetic defects or deletions may affect one or more globin genes, a variety of clinical phenotypes may be encountered. Heterozygotes (thalassaemia carriers) enjoy partial protection against malaria, with consequential survival advantage. This explains the unexpectedly high gene frequencies found in malaria-endemic areas. South Africa is not a malaria-endemic area, and therefore has a predictably low prevalence of thalassaemia and other inherited Hb disorders. However, because of migration, these conditions are increasingly encountered in countries not endemic to malaria. In this issue (part 1 of the 2-part CME series), discussion is centred around epidemiology, pathophysiology, clinical features and diagnosis. Management is discussed in the next issue (part 2).