Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is characterised by small vessel inflammation frequently involving the kidney with autoantibodies against neutrophil antigens leukocyte proteinase 3 (PR3) or myeloperoxidase (MPO) [89]. The gene discussed is MPO; the disease is anti-neutrophil cytoplasmic antibody-associated vasculitis.