CLASSIFICATION AND MANAGEMENT OF NECROTIZING VASCULITIDES

Systemic vasculitides are a heterogeneous group of diseases, Having on ly a partial understanding of the aetiologies and pathogenetic mechani sms of these disorders explains the difficulties encountered in classi fying and treating patients. Nevertheless, some important points have been established. Classification is mainly based on the size of vessel s affected and, from the polyarteritis nodosa group, microscopic polya ngiitis (MPA) has been separated from classic polyarteritis nodosa (c- PAN), The latter is a rare disease which is, in a small number of case s, the consequence of hepatitis B or C virus (HBV/HCV) infection. In t he other cases of c-PAN and in MPA, the aetiology is unknown as for Ch urg-Strauss syndrome (CSS) and Wegener's granulomatosis (WG). MPA, CSS and WG are mainly antineutrophil cytoplasmic antibodies (ANCA)-relate d vasculitides. ANCA play a part in the pathogenesis of diseases and a re sometimes useful markers for diagnosis and follow-up. Vasculitis tr eatments should be chosen according to classification, aetiology, path ogenetic mechanisms, severity and predictable outcome. In virus-associ ated vasculitides, treatment is based on the combination of antiviral agents and symptomatic or immunomodulating therapies, HBV-related PAN and HCV-related cryoglobulinaemia respond to interferon-a and to plasm a exchange. Responses are excellent in HBV-PAN but usually partial in HCV-cryoglobulinaemia, and relapses occur in the majority of cases. MP A, c-PAN, WG and other vasculitides respond to corticosteroids and cyt otoxic agents, mainly cyclophosphamide. Treatment duration and ways of administration can vary from one disease to another. Plasma exchange is not recommended as the First-line treatment. Immunoglobulins and ot her immunomodulating treatments are indicated in limited cases and the ir indications necessitate further prospective studies.