Rheumatoid arthritis (RA) is a long-term autoimmune condition that causes joint inflammation, resulting in pain, tenderness, expansion, and even joint malformation. It mostly causes inflammation and thickening of the synovium, the membrane that lines the joints. Joint erosion, cartilage breakdown, and function loss are all possible outcomes of RA over time. Though it can affect any joint in the body, it usually affects the smaller joints in the hands and feet. A significant role can be played by genetic ability in the progress of rheumatoid arthritis. The review's subject, "PTPN22" (sometimes referred to as "LYP in humans or PEP in mice"), is the typical non receptor PTP belonging to the proline rich subgroup of Type I. PTPN22 is a "major negative regulator of T-cell receptor (TCR) signal transduction" which is mostly express in the immune cells. Interestingly, a mutation in this gene has been related to the onset of many autoimmune disorders. Several genetic variants have been identified that contribute to the risk of developing RA, including rs2476601. This review discussed the PTPN22 as master regulation of immune system and the role of rs2476601 in RA.