PTPN22 and type 1 diabetes mellitus: Gain-of-function variant in PTPN22 (frequency in CEU = 0.12) was previously identified as being associated to different autoimmune disorders, such as RA, Hashimoto’s thyroiditis, Graves’ disease, type 1 diabetes (T1D), systemic sclerosis, and systemic lupus erythematosus64.