SOAT1 and rheumatoid arthritis: PTPN2 encodes for the ubiquitously expressed T cell protein tyrosine phosphatase (TCPTP), a JAK/STAT and growth factor receptor phosphatase that has been linked with the pathogenesis of type 1 diabetes mellitus, rheumatoid arthritis and Crohn’s disease by GWAS findings of non-coding SNP associations.