PRTN3 and anti-neutrophil cytoplasmic antibody-associated vasculitis: Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) constitutes a group of rare diseases characterised by necrotising inflammation of small blood vessels and the presence of ANCA [1], usually directed against myeloperoxidase (MPO) or proteinase-3 (PR3) [2,3].