Tehran University of Medical Sciences International Journal of Hematology-Oncology and Stem Cell Research 2008-2207 16 1 2022 01 02 47 54 Mozhgan Hashemieh Department of Pediatric Hematology Oncology, Imam Hossein Medical Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran Zahraalsadat Saadatmandi Department of Pediatric Hematology Oncology, Imam Hossein Medical Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran Azita Azarkeivan Iranian Blood Transfusion Research Center, High Institute for Research and Education in Transfusion Medicine, Thalassemia Clinic, Tehran, Iran Hossein Najmabadi Genetics Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran 2020 07 13 2021 05 01 Background: Thalassemia syndromes are the most prevalent hereditary hemoglobinopathies in the world. Iran is located on the thalassemia belt.  In this study, the effect of Xmn -1 polymorphism and coinheritance of alpha mutations on age at first transfusion as well as transfusion interval in Iranian thalassemic patients with homozygous Intervening Sequence (IVS) 1-5 mutation was assessed. Materials and Methods: In this retrospective cross-sectional study, 154 transfusion-dependent thalassemia (TDT) patients (140 patients with β-thalassemia major and 14 cases with β-thalassemia intermedia) who were homozygote of IVS 1-5 mutation participated. Blood samples were collected from participants using EDTA containers for genomic DNA analysis. DNA extraction and amplification-refractory mutation to determine the Xmn -1 polymorphism were performed. Multiplex Polymerase Chain Reaction (PCR) was performed to identify alpha globin deletions.  Results: The mean age of participants was 29±7 years. Fifty-eight participants were male and 96 were female. A significant relationship between the presence of Xmn -1 polymorphism and age at receiving first transfusion was detected. Coinheritance of alpha thalassemia mutation did not have a significant effect on age at first transfusion or transfusion interval. Conclusion: The presence of Xmn -1 polymorphism can delay the onset of transfusion in patients with homozygote IVS 1-5 mutation. https://ijhoscr.tums.ac.ir/index.php/ijhoscr/article/view/1388 https://ijhoscr.tums.ac.ir/index.php/ijhoscr/article/download/1388/900