Screening and genetic diagnosis of haemoglobinopathies.

The haemoglobin disorders are a group of autosomal recessive disorders characterized by either the reduced synthesis of one or more normal globin chains (the thalassaemias), the synthesis of a structurally abnormal globin chain (the haemoglobin variants) or in a few cases by both phenotypes (the reduced synthesis of a Hb variant, e.g. Hb E). They are the commonest single-gene disorders known and approximately 1000 different mutant alleles have now been characterized at the molecular level. The mutations are regionally specific, with each country having its own unique spectrum of abnormal haemoglobins and thalassaemia mutations, and can occur at high gene frequencies in some ethnic groups 1. Although haemoglobinopathy mutations are rarely found in individuals of North European origin, the number of immigrants in the North European countries is steadily increasing and the variety of their ethnic origins poses a problem for screening and accurate diagnosis.