evaluation of xmn1-158 yg variant in b-thalassemia intermediate patients in south-east of iran

background: xmn-1 polymorphism of y g globin gene ( hbg2 ) is a prominent quantitative trait loci (qtl) in β-thalassemia intermediate (β-ti). in current study, we evaluated frequency of xmn-1 polymorphism and its association with β-globin gene ( hbb ) alleles and hb f level in β-ti patients in sistan and balouchestan province, south-east of iran. methods: 45 β-ti patients were enrolled. hbb gene mutations and xmn-1 polymorphism were determined by amplification-refractory mutation system (arms) pcr method. hemoglobin profile was determined using capillary electrophoresis. results: males and females comprised 26 (58%) and 19 (42%) subjects respectively. mean age of the patients was 10.7±3.1 years old. overall, xmn-1 polymorphism was observed in 28 (62%) patients.  homozygous (tt) and heterozygous (ct) genotypes of the polymorphism represented with frequencies of 12 (26%) and 16 (35%) respectively.  main recognized hbb gene mutation was ivsi-5(g>c) with homozygous frequency of 44%.  non-zero (β + )alleles of hbb gene constituted 11.1 % (4 patients with heterozygous β + and one with homozygous β + genotype). hb f level was significantly higher in patients with at least one xmn-1 allele (67.9 ± 17.9%) than those without the polymorphism (19.5±20.3%, p<0.0001). also, patients with homozygous genotype demonstrated significant higher hb f compared to heterozygous (ct) cases (respective percentages of 85 ± 6.8 and 54.7 ± 10.5, p<0.0001). conclusion: our results highlighted the role of xmn-1 polymorphism as the main phenotypic modifier in β-ti patients in sistan and balouchestan province.