Tehran University of Medical Sciences Acta Medica Iranica 0044-6025 52 6 2014 06 15 418 423 EN Hossein Ali Ghlichnia Department of Neurology, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran. AND Department of Neurogenetics, Iranian Center of Neurological Research, Tehran, Iran. Abolghasem Kollaee Department of Neurogenetics, Iranian Center of Neurological Research, Tehran, Iran. AND Department of Medical Genetics, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran. Majid Gaffarpoor Department of Neurogenetics, Iranian Center of Neurological Research, Tehran, Iran. Abolfazl Movafagh Department of Medical Genetics, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Babak Ghlichnia Department of Neurogenetics, Iranian Center of Neurological Research, Tehran, Iran. Mahdi Zamani Department of Neurogenetics, Iranian Center of Neurological Research, Tehran, Iran. AND Department of Medical Genetics, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran. 2015 10 11 Multiple Sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system. It is a clinically heterogeneous disorder especially in terms of disease severity. Current investigations suggest that genes and gene-gene interactions not only influence on susceptibility to MS but also affect the disease severity. In this study, we investigated the contribution of the HLADRB1*1501 allele and single nucleotide polymorphism (SNP) in CD24 gene and also combined genotypes of the HLADRB1*1501 and CD24 SNP to disease severity in Iranian MS patients. We have reported previously that the HLA- DRB1*1501 allele and the CD24v/v genotype associated with disease susceptibility and some other studies proposed that HLA-DRB1*1501 allele be associated with MS severity. In this study, the results showed a significant difference in the Multiple Sclerosis Severity Score (MSSS) of the nine different genotypes (F=2.838, P=0.007). Subsequent analysis revealed a statistically significant difference in the MSSS between the MS patients who were carriers of HLA-DRB1*1501/1501 and those who were not carriers of HLA-DRB1*1501/1501 genotypes (P=0.04). Moreover, the MS patients carrying combined genotypes of the HLA- DRB1*1501/x-CD24 v/v had statistically severe disease than the patients who did not carry the HLA- DRB1*1501- CD24 v/v (P=0.047). In conclusion, our findings suggest that, HLA-DRB1*1501/1501 and bigenic genotypes of the HLA- DRB1*1501/x- CD24 v/v may influence on disease severity in Iranian MS patients. https://acta.tums.ac.ir/index.php/acta/article/view/4786 https://acta.tums.ac.ir/index.php/acta/article/download/4786/4452