Our data on 114 Iranian individuals with thalassemia intermedia phenotype revealed homozygous or compound heterozygous beta-globin mutations to be the predominant disease factor in 86.2% of cases. However, 8.2% of these individuals were found to be heterozygous or wild type for beta-globin mutations. In search for determinants outside of the beta-globin gene, which could be responsible for the unexpected thalassemia intermedia phenotype in these subjects, we screened the alpha-globin genes, the 5'HS3 and 5'HS4 regions of the beta-globin LCR, and the NF-E2 transcription factor for sequence variations in selected individuals. The -3.7 deletion was the only alpha-globin mutation detected, and no alterations were found in 5'HS3 and NF-E2. Sequence analysis of the 5'HS4 LCR core region identified three known SNPs in a single patient, who required irregular blood transfusions. The A/G polymorphism in the 5'HS4 palindromic region was also observed to be variable. Family studies were carried out on a female G/G homozygous patient, who received irregular blood transfusions. Her father, who had the same heterozygous IVSII-1 beta-globin mutation but the A/G genotype at the 5'HS4 palindromic site, presented with mild anemia and no requirement for blood transfusions. This suggests an impact of SNPs in the 5'HS4 LCR core region on the thalassemia phenotype and offers an interesting subject for further investigations in the Iranian population.
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