PTPN22 and type 1 diabetes mellitus: The PTPN22 allele C1858T has a single amino acid substitution R620W (arginine to tryptophan; rs2476601, OR= 1.890), and has been associated with T1D, Hashimoto’s thyroiditis, rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), vitiligo and Graves disease (82).