This group of systemic vasculitis includes granulomatosis with polyangiitis (GPA), primarily associated with antibodies to PR3–ANCA and microscopic polyangiitis (MPA) and eosinophilic granulomatosis with polyangiitis (EGPA), both principally associated with antibodies to MPO–ANCA. This evidence concerns the gene PRTN3 and eosinophilic granulomatosis with polyangiitis.