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