In 1985 van der Woude et al. reported the strong association of ANCA producing a diffuse granular cytoplasmic staining pattern on ethanol-fixed neutrophils (C-ANCA) and granulomatosis with polyangiitis (GPA) (formerly known as Wegener's granulomatosis (WG)) [3, 4]; a few years later, ANCA producing a perinuclear fluorescent pattern (P-ANCA) on the same cellular substrate were described in patients with idiopathic necrotizing crescentic glomerulonephritis and microscopic polyangiitis (MPA) [5]. This evidence concerns the gene PRTN3 and microscopic polyangiitis.