Diagnosis and evaluation of vasculitis.

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 [e.g. in the wide variety of signs and symptoms. Clinically the systemic vasculitides range from benign, locoregionANCA in Wegener’s granulomatosis (WG)] and immunohistological findings (e.g. IgA-dominant immune ally restricted processes (e.g. cutaneous leucocytoclastic angiitis) to systemic vasculitis leading to life-threatening deposits in Henoch–Schönlein purpura) which are specific for certain diseases and were described by conditions [e.g. pulmonary renal syndrome in antineutrophil cytoplasmic antibody (ANCA)-associated vascuJennette 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 in common extensive experience with diagnosing vascuscheme of primary systemic vasculitides (Table 1). 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 Immunopathogenesis have a very different prognosis and require different therapies. For example, a patient with purpura caused Most of the vasculitic syndromes are mediated by immunoby Henoch–Schönlein purpura has a clearly better progpathogenic mechanisms (‘immune vasculitides’) and nosis and needs less aggressive therapy than a patient most ‘immune vasculitides’ are idiopathic (= ‘primary’ with purpura caused by microscopic polyangiitis vasculitis). The immunopathogenic mechanisms of vas(MPA), which is likely to progress to life-threatening culitides have been classified into the four types of organ failure if not treated by immunosuppressives. So, hypersensitivity reaction described by Coombs and Gell in addition to the clinical picture, one needs to take into [35]; this classification was reviewed recently [5]. account the histology and immune phenomena in the Accordingly, clinicopathological and immunohistoblood and tissues, and a broader differential diagnosis chemical studies have led to the terms allergic angiitis to avoid missing secondary vasculitides or vasculitis-like (I ), antibody-mediated angiitis, including the ‘new’ syndromes (Table 2). group of ANCA-associated vasculitides (II ), immune complex vasculitis (III ), and vasculitis associated with T-cell-mediated hypersensitivity (IV ) (Table 4). Classification Eosinophilia and elevated IgE in the blood and tissues In 1952, Zeek [34] became the first author to incorporate (in situ) are characteristically associated with allergic a clinicopathological assessment based on the size of the angiitis and granulomatosis (‘Churg–Strauss syndrome’; vessels involved in the inflammatory process in her CSS); in ‘ANCA-associated vasculitides’ (AAV ) few or classification of necrotizing vasculitis. A number of no immune deposits are found in situ (‘pauci-immune alternative classification systems were proposed later vasculitis’). By contrast, immune complex deposits in situ are the hallmark of immune complex vasculitis, which is frequently associated with low complement Submitted 20 September 1999; revised version accepted 19 levels. Granulomatous arteritis is characterized by an October 1999. Correspondence to: W. L. Gross. inflammatory infiltrate induced by Th1 cells. The