Recently, it was reported the single nucleotide polymorphism (SNP), R620W (rs2476601), in PTPN22 increased susceptibility to several autoimmune diseases including rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), and insulin dependent diabetes mellitus (IDDM) [11-15]. This evidence concerns the gene PTPN22 and type 1 diabetes mellitus.