Thalassaemias and Other Haemoglobinopathies

The haemoglobinopathies are a heterogeneous group of autosomal recessive disorders caused by defects in the human globin genes. The disorders consist of the thalassaemias, characterised by either the reduced synthesis of one or more of the globin chains, and the haemoglobin variants, characterised by the synthesis of a structurally abnormal globin (Weatherall and Clegg, 2001). They form the most common single gene disorder in the world, and are found at high frequencies in many populations as a result of positive selection pressure due to falciparum malaria (see Chapter 24). Individuals with the carrier state are easily identifiable, permitting the control of the serious haemoglobinopathies by a programme of carrier screening, counselling and prenatal diagnosis (Petrou and Modell, 1995). The most important disorders for which prenatal diagnosis is considered are β°-thalassaemia, s-thalassaemia, sickle cell anaemia and the various compound heterozygous states that result in a clinically significant disease.