However, some patients with systemic vasculitis (other than CF-associated forms) are negative for both anti-PR3 and anti-MPO, while they are positive for anti-bactericidal permeability increasing protein (BPI) ANCA, suggesting that the presence of the latter may be involved in the pathogenesis of this disease, too (26, 27). This evidence concerns the gene PRTN3 and necrotizing vasculitis.