Immune complex vasculitis and polyarteritis nodosa

At a glance

• Chapel Hill 2012 names vasculitis by the largest vessel usually involved. This note covers medium-vessel PAN and the immune complex small-vessel group. ANCA vasculitis is in its own note; GCA in PMR and GCA.
• Immune complex vasculitis deposits immunoglobulin and complement in vessel walls. Biopsy immunofluorescence shows it. Complement is often low (except IgA vasculitis).
• PAN is necrotising arteritis of medium arteries, ANCA negative, with no glomerulonephritis. Think of it with mononeuritis multiplex, livedo, testicular pain and gut ischaemia.