Recently, however, an association between the minor allele (T) of a missense single-nucleotide polymorphism (SNP; R620W (rs2476601, 1858C/T)) in the protein tyrosine phosphatase non-receptor type 22 gene (PTPN22) and susceptibility to RA has been described [5]; this has been confirmed in several large cohorts of patients and controls [6-18]. This evidence concerns the gene PTPN22 and rheumatoid arthritis.