Vasculitis is inflammation of a vessel wall. The systemic and a major break was made in the 1990s with the 1990 American College of Rheumatology criteria (ACR 1990 vasculitides represent a highly heterogeneous group of clinicopathological entities. Vasculitis has many causes, criteria); and the elaboration of a uniform terminology for naming, defining, classifying and diagnosing vascualthough it produces only a few histological patterns of vascular inflammation. The clinical expression depends litic disorders at the Chapel Hill Conference 1992 (1992 CHC definitions). The 1990 ACR criteria were reviewed on the site, type and size of vessels involved. Vessels of any type in any organ can be affected, which is reflected in 1996 by Hunder [3]. The 1992 CHC definitions now include immunodiagnostically significant markers [eg in the wide variety of signs and symptoms. Clinically the systemic vasculitides range from benign, locoregion- ANCA in Wegener’s granulomatosis (WG)] and immunohistological findings (eg IgA-dominant immune ally restricted processes (eg cutaneous leucocytoclastic angiitis) tosystemicvasculitisleadingtolife-threatening deposits in Henoch–Schönlein purpura) which are specific for certain diseases and were described by conditions [eg pulmonary renal syndrome in antineutrophil cytoplasmic antibody (ANCA)-associated vascu- Jennette et al.[4]. The major problem with previous classification schemes was the lack of standardized diaglitis]. Many patients develop their disease against a background of non-specific symptoms, such as malaise, nostic terms and definitions. As a consequence, different names had been applied to the same disease and the weight loss, fever and night sweats (so-called B-symptoms), which reflect constitutional symptoms. same name to different diseases. Therefore, the CHC committee—comprised of internists, rheumatologists, More specific symptoms derive from the type of vessels involved; this has led to the well-known classification nephrologists, immunologists and pathologists who have incommonextensiveexperiencewithdiagnosingvascuscheme of primary systemic vasculitides (Table1). However, in clinical practice vasculitic syndromes do litides—proposed the names and definitions given in Table 3. not respect vessel size boundaries. In addition, discrete vasculitides with indistinguishable clinical presentations due to the predominant involvement of small vessels