MPO and anti-neutrophil cytoplasmic antibody-associated vasculitis: In Asian countries, the prevalence of MPO/PR3-ANCA in patients with ANCA-associated vasculitis (AAV) is much higher than in European countries [22,23], but there has been no report about MPO-ANCA-associated vasculitis in ADPKD patients or any association between MPO-ANCA and ADPKD.