PTPN22 and juvenile idiopathic arthritis: A PTPN22 missense mutation R620W (c.1858C > T, p.Arg620Trp) has been associated with an increased risk of several autoimmune disorders, such as SLE, type 1 diabetes mellitus (T1DM), vitiligo, RA, and finally JIA, probably by not promoting type 1 IFN-driven inhibition of inflammation [91,94,95,96,97,98,99].