GPA is typically associated with proteinase 3 (PR3) epitopes, while other entities like microscopic polyangiitis (MPA) and eosinophilic granulomatosis with polyangiitis (EGPA) are linked to myeloperoxidase (MPO)-ANCA or negative ANCA [3]. The gene discussed is MPO; the disease is eosinophilic granulomatosis with polyangiitis.