In a population-based, case-control study, MPO-ANCA specificity was significantly more common than PR3-ANCA specificity among AAV patients with high exposure to silica (67% of MPO-ANCA patients were classified as having high exposure versus 40% of PR3-ANCA patients, p = 0.02) [20]. Here, MPO is linked to anti-neutrophil cytoplasmic antibody-associated vasculitis.