PTPN22 and rheumatoid arthritis: RA genetic studies have reported polymorphisms PTPN22 (R620W, rs2476601) [9,11-16], CTLA-4 (CT60, rs3087243) [17,18], and PADI-4 (PADI4_94, rs2240340) [8] to be associated with increased risk for RA.