Immunological tests confirmed ANCA-associated vasculitis, and kidney biopsy showed ANCA-mediated pauci-immune glomerulonephritis supported by the salvage technique used by pronase immunofluorescence, which provides evidence against the glomerular disease of the complex immune type in the setting of MPO-ANCA seropositivity. The gene discussed is MPO; the disease is glomerulonephritis.