PTPN2 and rheumatoid arthritis: Further examination of RA genotyping showed that patient samples with both PTPN2:rs478582 and PTPN22:rs2476601 alleles (regardless of heterozygous or minor alleles) showed to be more significant (p-values ≤ 0.05) compared to healthy controls, showing a 6.5-fold increased risk of developing RA.