Solans Loqué R. et al. showed in a retrospective study on 450 Spanish patients with ANCA-associated vasculitis that anti-MPO antibody-positive patients had twice the risk of death and almost half the risk of relapse than those with anti-PR3 antibody-positive ANCA, supporting that serological classification is better than phenotypic classification in predicting the outcome of vasculitis [13]. The gene discussed is MPO; the disease is vasculitis.