Epidemiology of ANCA associated vasculitis

Sammendrag

ANCA associated vasculitis (AAV) comprises three syndromes with systemic vasculitis (Wegener’s granulomatosis (WG), Churg Strauss syndrome (CSS) and icroscopic polyangiitis (MPA)), which all involve small and medium sized vessels and are associated with antibodies against cytoplasmatic antibodies in neutrophils (ANCA). Polyarteritis nodosa (PAN) is included in this review as it also affects medium sized vessels, and has many clinical findings in common with the AAV.
Since the recognition of ANCA, increasing data have become available on the epidemiology of these vasculitidis. WG constitutes half of the AAV and its prevalence has increased from 30/million in the late 1980’s in the USA to 160/million in this century in northern Europe. The prevalence for the whole group of primary systemic vasculitides is now 300/million in Sweden. The annual incidence of WG increased from 6.0/million to 14/million during the 1990’s in Tromsø, but it is unknown if this is a true increase or the result of an increased awareness of the diagnosis. For the whole group of AAV, the annual incidence in most more recent studies is relatively constant over time and by geographical location, ranging from 13 to 21/million. Nonetheless there are interesting differences in the prevalence of specific vasculitis between different geographical areas, as well as for sub specificities of ANCA.
There seems to be a South-North gradient for WG and PR3-ANCA with high figures reported from northern Europe and southern New Zealand. In European studies WG is 90% PR3-ANCA positive. MPA which is predominantly MPO-ANCA associated are more frequent in the Mediterranean countries and also has an increasing gradient towards east-Asia, as almost all AAV in China and Japan are diagnosed as MPA, predominantly MPO-ANCA positive.
There are also some ethnic and gender differences. WG is most prevalent among Caucasians in the USA and in people with European ancestors in Paris and in New Zealand, less frequent in Africans and Asians. Several studies have shown that the highest incidence of WG is in males 60-70 years old. Females are younger at onset, and in children WG is most frequent in girls. With better treatment (cyclophosphamide and corticosteroids), the survival of AAV has increased considerably. However disease control is not optimal, as most of the vasculitis present a remitting-relapsing course and organ damage is considerable. Hence, we are still looking to improve treatment regimens