Investigation of the Frequency of CRP Gene Polymorphism in Rheumatoid Arthritis and Associations with CRP Level and Clinical Involvements of the Disease.

Introduction: The aim of this study was to compare the frequency of rs1205, rs1130864 and rs1800947 single nucleotide polymorphisms (SNPs) in the C-reactive protein (CRP) gene in rheumatoid arthritis (RA) patients and healthy controls. In addition, the aim was to investigate the association between these polymorphisms and serum CRP levels, Disease Activity Score-28 (DAS28) and clinical findings, especially extra-articular involvement such as interstitial lung disease. Methods: This single-center study included 120 patients with RA and 100 healthy controls. DAS28-CRP was used to measure disease activity. Interstitial lung disease was confirmed by ground-glass opacities and interstitial thickening on chest computed tomography (CT) and other CT findings. Peripheral blood samples were collected in tubes with EDTA for genotyping. After DNA extraction, SNPs were analyzed using TaqMan probe-based polymerase chain reaction. Results: Among the three CRP SNPs (rs1130864, rs1205, rs1800947), a significant difference was observed in the distribution of rs1130864 between RA patients and controls. TT homozygous and CT heterozygous genotypes were significantly lower in the patient group (p = 0.002). Furthermore, the TT genotype of rs1130864 was significantly associated with lung involvement in patients with RA (p = 0.017). No significant association was found between SNPs and baseline CRP levels and DAS28 scores. Conclusion: In our study, we found a significant association between CRP rs1130864 gene polymorphism and lung involvement in RA patients. To the best of our knowledge, this is the first study to evaluate this association. However, further studies with larger cohorts are needed to confirm these findings.