PADI4 and rheumatoid arthritis: Large-scale genome-wide association studies (GWAS) identified risk factors for RA and described to be risk loci for also other autoimmune diseases several SNPs in genes including: protein tyrosine phosphatase non-receptor type 22 (PTPN22, rs2476601), peptidylarginine deiminase type 4 (PADI4, rs2240340), tumor necrosis factor receptor-associated factor 1 (TRAF1, rs3761847), signal transducer and activator of transcription 4 (STAT4, rs7574865), and cluster of differentiation 40 (CD40, rs4810485) [4,6].