The anti-neutrophil cytoplasmic antibody (ANCA) associated vasculitides (AAV) are diseases in which autoimmunity to the neutrophil granule proteins myeloperoxidase (MPO) or proteinase-3 (Pr3) can cause multi-organ injury, including rapidly progressive glomerulonephritis. The gene discussed is PRTN3; the disease is anti-neutrophil cytoplasmic antibody-associated vasculitis.