MPO and vasculitis: ANCA is found in 30 to 47% of patients with anti-GBM disease and thus, histological evidence is of paramount importance for correct diagnosis of anti-GBM disease, because patients might be erroneously treated for ANCA-associated vasculitis.3 The pathogenic effects of anti-GBM was demonstrated by Lerner et al. through the induction of glomerulonephritis in monkeys.6 ANCA is also known to have pathogenic effects when binding to myeloperoxidase (MPO) or proteinase 3 (PR3) on the surface of primed neutrophils.