This review has excluded cases with ANCA-negative vasculitis, a subgroup of cases which is underrepresented in current research, and EGPA, which has a completely different etiopathogenesis when compared to cases with GPA (classically PR3-ANCA positive) or MPA (MPO-ANCA positive). This evidence concerns the gene PRTN3 and eosinophilic granulomatosis with polyangiitis.