Genetic Susceptibility and Disease Activity in Ankylosing Spondylitis: The Role of G Protein-Coupled Receptor 35rs4676410 Polymorphism in a Turkish Population

<b><i>Background:</i></b> Ankylosing spondylitis (AS) is a chronic inflammatory disorder with a significant genetic predisposition. Genome-wide association studies (GWAS) have identified immune-related loci, including the G Protein-Coupled Receptor 35 (GPR35) gene, as potential contributors to AS pathogenesis. This study aimed to evaluate the association between the rs4676410 polymorphism in the GPR35 gene and both AS susceptibility and disease activity in a Turkish population. <b><i>Methods:</i></b> This case-control study included 200 participants (100 AS patients and 100 healthy controls). DNA was isolated from blood samples, and the rs4676410 polymorphism was analyzed using real-time polymerase chain reaction (PCR). Disease activity in AS patients was assessed using the Bath AS Functional Index (BASFI), Bath AS Disease Activity Index (BASDAI), and disease activity scores including C-reactive protein (ASDAS-CRP) scores. Statistical analyses were conducted using IBM SPSS 26. <b><i>Results:</i></b> The rs4676410 polymorphism was significantly associated with AS susceptibility. The AA genotype and A allele were more prevalent in AS patients, indicating an increased risk of developing AS. Among disease activity measures, ASDAS-CRP scores were significantly higher in patients with the AA genotype (<i>p</i> = 0.043), while no significant differences were observed for BASFI and BASDAI scores across genotypes. <b><i>Conclusion:</i></b> The findings suggest that the rs4676410 polymorphism in the GPR35 gene is associated with AS susceptibility and may influence disease activity through elevated inflammatory responses. These results highlight the potential of the AA genotype and A allele as genetic markers for AS and underscore the importance of integrating genetic insights into personalized treatment approaches.