en علوم مولکولی Molecular Sciences تحقیقی Original article <em><strong>Background and objectives: </strong></em>Rheumatoid arthritis (RA) is an autoimmune disease with a complex genetic background. The protein tyrosine phosphatase non-receptor type 22 (PTPN22) is a lymphoid specific protein tyrosine phosphatase which is involved in negative regulation of T cell response. Several studies have assessed the association between PTPN22 single nucleotide polymorphisms (SNPs) with RA susceptibility. Here, we aimed to assess the association of PTPN22 (1858 C>T) variant with the susceptibility to RA in northeast of Iran.<br> <em><strong>Methods:</strong></em> A total of 127 RA patients and 119 age- and sex- matched healthy donors were enrolled. The polymerase chain reaction (PCR) followed by restriction fragment length polymorphism (RFLP) technique (PCR-RFLP) was applied to detect PTPN22 (1858 C>T) SNP. SPSS 22.0 software was used to analyze data using relevant statistical tests.<br> <em><strong>Results: </strong></em>Comparison of allele and genotype frequencies of PTPN22 (1858 C>T) SNP in RA patients and healthy donors revealed no significant association with RA susceptibility.<br> <em><strong>Conclusion:</strong></em> The present study suggests that the PTPN22 (1858 C>T) genetic variants are not associated with RA susceptibility and disease activity. While this is the first report from northeast of Iran, further studies are needed to confirm these findings Protein tyrosine phosphatase non-receptor type 22 (PTPN22), Rheumatoid arthritis, rs2476601 40 47 http://goums.ac.ir/jorjanijournal/browse.php?a_code=A-10-206-19&slc_lang=en&sid=1 Sahar Ghovanjzadeh 10031947532846004334 10031947532846004334 No Department of Biology, Gorgan Branch, Islamic Azad University, Gorgan, Iran Hadi Bazzazi hadi.bazzazi@gmail.com 10031947532846004335 10031947532846004335 Yes Department of Medical Laboratory Sciences, Gorgan Branch, Islamic Azad University, Gorgan, Iran Yaghoub Yazdani 10031947532846004336 10031947532846004336 No Infectious Diseases Research Center, Golestan University of Medical Sciences, Gorgan, Iran