PRTN3 and granulomatosis with polyangiitis: In GPA, the pattern of autoantibody staining of ethanol-fixed neutrophils is typically cytoplasmic (c-ANCA), rather than perinuclear (p-ANCA), due to the presence of antibodies against proteinase 3, which is a constituent of the azurophilic granules of the neutrophil [2, 3].