Molecular Basis of β-Thalassemia and Other Hemoglobinopathies in Bulgaria: An Update

β-Thalassemia (thal) is relatively common in Bulgaria. Over the past 40 years population studies have been carried out in most parts of the country. Different approaches for the detection of β-thal carriers were used and a frequency from 0.5 to 19.9% was found. We have been studying β-thal in Bulgaria since 1965 and, based on our results, the average frequency is 2.5%. Here we update our results on the molecular basis of β-thal and include some unpublished data. One thousand seven hundred and fifty-two patients with signs of hemolysis were studied. Among these, 723 patients (41.3%) had β-thal or a related condition. In addition, blood samples from 875 newborn babies were studied. Eighteen different β-thal alleles were identified. The codon 39 (C→T) and IVS-I-110 (G→A) mutations occurred most frequently, and seven additional mutations were observed that were present at frequencies of 2.4 to 14.2%. This broad spectrum of β-thal alleles complicates the analysis for institutions involved in prenatal diagnosis. The frequency of α-thal is low (0.5% α-thal-1 and 1.6% for α-thal-2).