Abstract
Haemoglobinopathies are the most common monogenic diseases, posing a major public health challenge worldwide. Cyprus has one the highest prevalences of thalassaemia in the world and has been the first country to introduce a successful population-wide prevention programme, based on premarital screening. In this study, we report the most significant and comprehensive update on the status of haemoglobinopathies in Cyprus for at least two decades. First, we identified and analysed all known 592 β-thalassaemia patients and 595 Hb H disease patients in Cyprus. Moreover, we report the molecular spectrum of α-, β- and δ-globin gene mutations in the population and their geographic distribution, using a set of 13824 carriers genotyped from 1995 to 2015, and estimate relative allele frequencies in carriers of β- and δ-globin gene mutations. Notably, several mutations are reported for the first time in the Cypriot population, whereas important differences are observed in the distribution of mutations across different districts of the island.
Highlights
The range of 15–18%6, one of the highest in the world
The spectrum of α-thalassaemia mutations has been well-documented over the last decades[13], with more than 230 mutations currently reported in the public IthaGenes database[1]
More than 350 β-thalassaemia mutations have been reported in the IthaGenes database[1]
Summary
The range of 15–18%6, one of the highest in the world. In addition, the α-thalassaemia carrier rate was estimated to be around 20%7, earlier studies using electrophoresis estimated it to be about 10–12% of the population[8,9]. Β-thalassaemia is characterised by the reduced synthesis (β+) or absence (βo) of the β-globin chains in the Hb molecule, resulting in accumulation of unbound α-globin chains that precipitate in erythroid precursors in the bone marrow and in the mature erythrocytes, leading to ineffective erythropoiesis and peripheral haemolysis[16]. It is mainly caused by single nucleotide substitutions, small deletions or insertions within the β-globin gene or its immediate flanking sequence and, rarely, by large deletions[17,18]. A novel δ-globin chain variant (Hb A2-Famagusta) was discovered in four distinct families in Cyprus[23], while other δ-globin variants have been observed in the past[21], with Hb A2-Yialousa being the most prevalent
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