α, β, δ and γ thalassaemias and related conditions

In thalassaemia, a significantly reduced rate of synthesis of one type of globin chain leads to unbalanced chain synthesis with excess of a normal globin chain contributing to the pathological effects. This chapter discusses the laboratory features and diagnosis of α, β, δ and γ thalassaemias and related conditions. The α thalassaemias are a group of conditions resulting from a reduced rate of synthesis of a globin. It can be a completely asymptomatic condition, resulting from deletion or dysfunction of one of the four a genes, or haemoglobin Bart's hydrops fetalis, usually resulting from deletion of all four a genes and consequent total lack of a globin synthesis. Since normal individuals have two allelic β globin genes, β thalassaemia can exist in a heterozygous or homozygous state. δ thalassaemia is of significance in relation to diagnosis of β thalassaemia trait. γ thalassaemia condition is manifest maximally during intrauterine life.