The R620W (C1858T, rs2476601) polymorphism in PTPN22 exon 14 was first associated with type 1 diabetes [18] and subsequently with other autoimmune disorders such as rheumatoid arthritis, systemic lupus erythematosus, and systemic sclerosis [19-21]. Here, PTPN22 is linked to systemic lupus erythematosus.