Vasculitis.

The systemic vasculitides are a group of rare inflammatory conditions resulting in inflammation and necrosis of blood vessel walls. They are somewhat commoner than previously believed with an annual incidence approaching 40 per million. Furthermore the annual incidence of rheumatoid vasculitis is 12.5 per million and Wegener's granulomatosis is 8.5 per million. The first useful classification system for systemic vasculitis was published in 1952, since then a number of different schemes have been published. The major changes have been the recognition of the importance of dominant blood vessel size, the distinction between primary and secondary vasculitis and the incorporation of pathogenetic markers such as ANCA (see Table 6). Until relatively recently there were no widely agreed diagnostic or classification criteria. In 1990 the ACR published criteria for the diagnosis of polyarteritis nodosa, Churg-Strauss syndrome, Wegener's granulomatosis, hypersensitivity vasculitis, Henoch-Schönlein purpura, giant cell arteritis and Takayasu's arteritis. The criteria were provided in both traditional and tree format. Sensitivity and specificity rates varied considerably: 71.0-95.3% for sensitivity and 78.7-99.7% for specificity. The criteria were not tested against the general population or against patients with other connective tissue diseases or rheumatic conditions. In 1993/94 the Chapel Hill Consensus Conference developed and published definitions for the nomenclature of systemic vasculitis based on clinical features. These have not met with universal acceptance. However, they are a useful addition, since their use should result in different centres studying more homogeneous populations of patients and facilitate comparison of data between different centres. Assessment of vasculitis comprises an activity score (BVAS), damage index and quality of life/health status (SF-36). These are recent developments which are still undergoing validation.