While the MHC constitutes the strongest association in vasculitis, there are several loci outside the MHC, including SERPINA1, PRTN3, SEMA6A, PTPN22, CTLA4, FCGR3B, and ARPC1B that have also been established as genetic risk factors for these diseases, coding for immunological molecules that increase susceptibility to autoimmunity (36) (Table 1). Here, ARPC1B is linked to vasculitis.