Association of the PTPN22 gene polymorphism with autoantibody positivity in Turkish rheumatoid arthritis patients

The PTPN22 C1858T gene polymorphism has been recently reported to be associated with rheumatoid arthritis (RA) in European and North American ancestry. In contrast, the frequency of PTPN22 C1858T polymorphism is extremely rare in Asian and African populations. As the genetic heterogeneity between populations is clearly present in RA, we wanted to investigate whether the PTPN22 C1858T polymorphism is associated with RA in Turkey and with autoantibody positivity. A total of 323 RA patients and 426 healthy controls were genotyped by polymerase chain reaction restriction fragment length polymorphism for the PTPN22 C1858T polymorphism (rs2476601). The frequencies of heterozygote genotype (CT) were 8.4% in RA patients and 5.4% in the healthy controls, respectively [odds ratio (OR): 1.6, P = 0.14]. The homozygote genotype (T/T) was absent in both RA patients and the healthy controls. When compared with the healthy controls, we found the significant associations between the frequency of PTPN22 heterozygote (CT) polymorphism and RA patients with RF positivity and anti-CCP positivity, respectively (OR: 2.05, P = 0.04 and OR: 2.1, P = 0.03, respectively). Our study suggests that the PTPN22 C1858T polymorphism acts as a susceptibility gene for autoantibody-positive RA in Turkey.