[Vasculitis and its renal manifestation with special reference to anti-neutrophil cytoplasmic antibody]

The nomenclature and classification of vasculitis have been problematic, with each researcher proposing their own system. Since the discovery of anti-neutrophil cytoplasmic antibody and the consensus conference on the nomenclature of vasculitis in Chapel Hill, order has been brought to the chaos to some extent. Measurement of P-ANCA and C-ANCA in patients' sera has exerted an immeasurable influence on the clinical aspects of vasculitis, since they are shown to be valuable for the diagnosis and assessment of the vasculitic activity in most cases. Pathogenetic significance is also given to ANCA. ANCA has been reported to release myeloperoxidase(MPO) and proteinase-3 antigens from neutrophils activated by inflammatory cytokines. When both MPO antigen in serum as well as ANCA were measured serially in the same patients, however, clinical condition was better reflected by the amount of serum MPO than the titer of ANCA in some patients. Thus, the amount of serum MPO increased without concomitant rise in ANCA titer in exacerbation of vasculitis in one patient. In two more, high serum titers of ANCA and low MPO antigen in the active phase of vasculitis were reversed when pulmonary hemorrhage occurred, and fatal outcome ensued. It could be speculated from these observations that some ANCA might be directed against the active sites of MPO and even suppress the vasculitic activity through blocking MPO. Since definitive evidence has not been obtained so far on the pathogenetic role of ANCA, the clinical significance of ANCA should be addressed at the same level as anti-dsDNA antibody in systemic lupus erythematosus: aid for diagnosis and disease activity.