Molecular Basis of β-thalassaemia in Bulgaria. An Update

Abstract

�-thalassaemia is a relatively frequent inherited condition in the Mediterranean countries, especially on the Balkan Peninsula, and the incidence of �thalassaemia among Bulgarians has been estimated to 2.5%. Our purpose was to update the knowledge on the molecular basis of �thalassaemia in Bulgaria and include some unpublished data. The study was carried out at the University Children’s Clinic; University Eye Clinic; Trakia University – Stara Zagora, Bulgaria; Eye Hospital “Prof. Pashev”, Sofia, Bulgaria; Research Centre for Genetic Engineering and Biotechnology, Macedonian Academy of Science and Arts, Scopje, Republic of Macedonija; International Reference Laboratory for Haemoglobinopathies (IRLH) and for a period of 45 years 1752 patients were studied. The inclusion criteria were clearly defined. The most common form found is heterozygous �-thalassaemia. The ratio between the frequencies of � 0 and � + -thalassaemia genes is 2:1, based both on the data for phenotypic expression and on molecular characterasation of thalassaemia genes. About half of all �-thalassaemia chromosomes have either the codon 39 (C!T) or the IVS-I-110 (G!A) mutations. Five additional mutations (IVS-I-1, cod 5, IVS-I-6, cod 6 and cod 8) occur at a frequency of 4 to 14%. During the period of investigations two new hiperunstable haemoglobins named Hb Stara Zagora and Hb Yambol were found.