The Spectrum of β-Thalassemia Mutations in Siirt Province, Southeastern Turkey

Abstract

β-Thalassemia (β-thal) is the most common hereditary genetic blood disorder. The aims of this study were: (i) to determine the mutation types and the frequency of these mutations in β-thal patients to obtain the ethnic origins of the population in Siirt Province; (ii) to evaluate the pathogenicity of these mutations by performing in silico analysis; (iii) to reveal the genotype-phenotype correlation by comparing the clinical manifestation of our patients to the specific mutations in this population. This study included 34 patients (18 males and 16 females) with a mean age of 9.1 ± 3.6 years (range 3–16 years). All mutations were determined using sequence analysis methods, and the mutations were analyzed using bioinformatics tools. Thirteen different mutations were detected in the patients: IVI-I-110 (G>A) (HBB: c.93-21G>A) (38.9%); IVS-II-1 (G>A) (HBB: c.315_1G>A) (11.1%); –30 (T>A) (HBB: c.-80T>A) (9.25%) and IVS-I-1 (G>A) (HBB: c.92 + 1G>A) (9.25%), were the most common, and these mutations constituted 68.5% of the cases. Missense codon 6 (A>T) (HBB: c.20A>T) was not pathogenic; however, all the intronic mutations (IVS-I-1, IVS-I-110, IVS-II-1) and frameshift mutations [codon 44 (–C) (HBB: c.135delC) and codons 36/37 (–T) (HBB: c.112delT)] resulted in disease. These mutations can be used to determine the ethnic origin of the Siirt population and, in affected pregnant women, to develop prenatal strategies. A fatal phenotype can be identified by in silico analysis; however, mutations that are unknown prior to marriage, pregnancy, and childbirth or new mutations can be less accurately identified.