They are generally divided into proteinase-3 (PR3), specific for Granulomatosis with Polyangiitis (GPA); Myeloperoxidase (MPO), more specific for Microscopic Polyangiitis (MPA) and Eosinophilic Granulomatosis with Polyangiitis (EGPA); and atypical ANCA [87]. The gene discussed is MPO; the disease is eosinophilic granulomatosis with polyangiitis.