Advances in pathogenesis and treatment of ANCA-associated vasculitis.

Anti-neutrophil cytoplasmic autoantibodies (ANCA) directed to proteinase 3 (PR3-ANCA) and myeloperoxidase (MPO-ANCA) are sensitive and specific markers for their associated diseases, granulomatosis with polyangiitis (GPA, formerly Wegener's granulomatosis) and microscopic polyangiitis (MPA), respectively. Clinical observations suggest but do not prove that ANCA are involved in the pathogenesis of GPA and MPA. In vivo and in vitro experimental data strongly suggest if not prove that MPO-ANCA underlie the pathological lesions seen in MPO-ANCA associated MPA. This is less clear for PR3-ANCA associated GPA in which, besides small-vessel vasculitis, granulomatous inflammation is apparent. Here, cellular immunity appears to play an additional role. Insight into the pathogenetic events involved in these diseases has resulted in new ways of treatment that target the specific pathways that underlie the development of the lesions.