Genes of importance in ACPA-positive RA include those encoding protein-arginine deiminase type 4 (PADI4), tyrosine-protein phosphatase non-receptor type 2 (PTPN22), cytotoxic T-lymphocyte protein 4 (CTLA4), interleukin-2 receptor subunit α (IL2R α), and signal transducer activator of transcription (STAT4) [15]. This evidence concerns the gene PADI4 and rheumatoid arthritis.