α-Thalassaemia

α-Thalassaemia

Definition

Inherited haemoglobinopathy with defective synthesis of the α-globulin genes. It is mainly found in the Far East, Middle East and Africa.

Aetiology

α-Thalassaemia is caused by gene deletions. There are four copies of the α gene, two on each chromosome 16. Deletion may be of one or both α chain genes on each of the chromosomes.

Clinical features

·        Deletion of all four copies of the α gene (–/–) prevents production of any viable haemoglobin. This disorder is also termed haemoglobin Bart’s (γ4) hydrops syndrome and results in a stillbirth or neonatal death.

·        Deletion of three genes (–/α-) causes HbH disease (a moderate anaemia with splenomegaly and the production of HbH (β4) from the excess β chains). Treatment is not usually required.

·        Deletion of one (-α/αα) or two genes (-α/-α or –/αα) causes α-thalassaemia trait in which there are microcytic red blood cells with or without a mild anaemia.

Investigations

Full blood count shows microcytosis with or without anaemia. The diagnosis may be confirmed by quantitative globin chain synthesis.