The chains produced in excess precipitate in the cell, forming Heinz bodies. Heterozygotes have thalassaemia minor, a condition in which there is usually mild anaemia and little or mo clinical disability. The diagnostic features are listed in the information box. Beta-thalassaemia minor is often detected only when iron therapy for a mild microcytic anaemia fails. The diagnostic features are also summarized in the information box.
Symptoms are absent or mild.
Intermediate grades of severity occur. The treatment of beta-thalassaemia major is given in Table 11.11. It is possible to identify a fetus with bomozygous beta-thalassaemia by obtaining chorionic villus material for DNA analysis sufficiently early in pregnancy to allow termination of pregnancy. The reduction or absence of albha chain synthesis is common in South-east Asia. There are two alpha gene loci on chromosome 16 and therefore four alpha genes.