δ-Thalassemia in Cyprus

Abstract

To help clarify the hematological picture of patients who may be positive for β- and δ-globin gene mutations, the following study was carried out. Our aim was to identify the δ-globin gene mutations found in the Greek Cypriot population, their frequencies and the Hb A₂ values associated with them. Seventy-four samples were selected from a random sample of 5,030 individuals, and the database of the Molecular Genetics Thalassaemia Department containing diagnostic analyses data was also mined for relevant information.

Four novel for Cyprus δ-globin gene mutations: −30 (T→C), Hb A₂-Wrens [δ98(FG5)Val→Met, GTG→ATG], IVS-I-2 (T→C) and Hb A₂-Yokoshima [δ25(B7)Gly→Asp (GGT→GAT)] were identified. Hb A₂-Yialousa [δ27(B9)Ala→Ser, GCC→TCC], Hb A₂-Yokoshima, Hb A₂-Troodos [δ116(G18)Arg→Cys, CGC→TGC], Hb A₂-Pelendri [δ141(H19)Leu→Pro, CTG→CCG], codon 4 [δ4(A1)Thr→Ile], codon 59 (−A), Hb A₂-Wrens, IVS-II-897 (A→G), IVS-I-2, −55 (T→C) and −30 bring the total to 11 δ-globin alleles found in the Greek Cypriot population. Hb A₂-Yialousa is the most common mutation followed by codon 4, with frequencies of 60.7 and 17.8%, respectively.

Hb A₂ levels above 1.9% have been found to indicate a significantly reduced possibility for the presence of a δ-globin gene mutation in this population. For Hb A₂ levels of 1.7 and 1.8% the possibility of a δ-globin gene mutation rises to 90.9% and reaches 100% for lower Hb A₂ levels. The frequency of all the mutant δ-globin chromosomes in the sample is 0.0067 and the carrier frequency is 1.26%.

Keywords:

• δ-Thalassemia (thal)
• δ-Globin
• Mutation
• Frequency
• Cypriot
• Hb A₂