STAT4 and rheumatoid arthritis: For example, genetic alterations in signal transducer and activator of transcription 4 (STAT4), tyrosine phosphatase non-receptor type 22 (PTPN22), cytotoxic T-lymphocyte associated protein 4 (CTLA4), peptidylarginine deiminases (PADI)-2, and PADI-4 have been reported to be associated with RA [8].