Since Botinni et al. first reported the association between PTPN22 gene variants and type 1 diabetes mellitus (T1DM), studies on other diseases such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), autoimmune thyroid diseases, and vitiligo have been published successively. This evidence concerns the gene PTPN22 and rheumatoid arthritis.