Juvenile idiopathic arthritis (JIA) is the most common chronic rheumatic disease in children. Genetics and inflammatory elements seem to act as major underlying factors in its pathogenesis. The aim of this study is to identify the associations between interleukin-6 (IL-6) gene polymorphisms and individuals' vulnerability to JIA in a group of Iranian pediatric patients. Fifty-four patients with JIA were enrolled in this investigation and compared with 139 healthy individuals. Using polymerase chain reaction with sequence-specific primers, cytokine genotyping was performed. The allele and genotype frequencies of two single nucleotide polymorphisms (SNPs) within the IL-6 gene at -174 and +565 positions were assessed. A significant positive association was observed for IL -6 -174 G allele in the patient group (p = 0.02). Furthermore, a positive association was observed in patients with JIA for the GG genotype at the same position (p < 0.01), thus revealing a predisposing effect in JIA patients. On the other hand, a significant negative association was found for IL-6 -174 CG genotype (p < 0.01) in the case group. No significant difference was discovered in both the allelic and genotypic frequencies of IL-6 +565 position between patients and controls. Additionally, haplotype analysis divulged over representation of IL-6 GG haplotype in patient group (p < 0.01) as well as IL-6 CG haplotype in healthy controls (p < 0.01). Certain allele, genotype, and haplotype in IL-6 gene were over expressed in patients with JIA, which probably could render individuals more susceptible to this disease.
Keywords: Children; Cytokine; Interleukin-6; Juvenile idiopathic arthritis; Single nucleotide polymorphism.