EPIDEMIOLOGY OF SYSTEMIC VASCULITIS - CHANGING INCIDENCE OR DEFINITION

The epidemiology of the systemic vasculitides is poorly documented. Ma ny studies have been conducted from tertiary referral centers, with re sulting problems of referral bias and uncertainty of denominator popul ation, or have involved small populations. We have estimated the incid ence of the major forms of systemic vasculitis in a stable, ethnically homogeneous population of 414,000 adults from 1988 to 1994. The overa ll annual incidence of systemic vasculitis (excluding giant cell arter itis) is 39/million (95% confidence intervals; ranging from 31 to 47). The annual incidence of Wegener's granulomatosis is 8.5/million (rang e, 5.2 to 12.9), Churg-Strauss syndrome 2.4/million (0.9 to 5.3), micr oscopic polyangiitis 2.4/million (0.9 to 5.3), adult Henoch-Schonlein purpura 1.2/million (0.3 to 3.5), and systemic rheumatoid vasculitis 1 2.5/million (8.5 to 17.7). These data suggest that the overall inciden ce of systemic vasculitis is greater than previously thought (10/milli on) with Wegener's granulomatosis and systemic rheumatoid vasculitis b eing the most common. Whether this represents a genuine increase in in cidence or increased physician awareness is uncertain. (C) 1995 by W.B . Saunders Company