Small vessel vasculitis

Abstract Small vessel vasculitis is vasculitis affecting predominately small intraparenchymal arteries, arterioles, capillaries, and venules. There are two main types: antineutrophil cytoplasmic antibody associated and immune complex mediated. The ANCA associated vasculitides are discussed in chapter 19.3 IgA vasculitis (IgAV) was formerly known as Henoch Schönlein purpura. The revised nomenclature reflects the importance of IgA vasculitis in pathogenesis. The Chapel Hill Consensus Conference defined IgA vasculitis as ‘vasculitis with IgA1-dominant immune deposits, affecting small vessels (predominantly capillaries, venules, or arterioles)’. IgA vasculitis often involves skin and gut, and frequently causes arthritis. Glomerulonephritis indistinguishable from IgA nephropathy may occur. Its aetiology is unknown, but it frequently occurs after an infection several days to weeks before. The most frequently isolated organism is beta-haemolytic streptococcus. Drugs such as a penicillin, ampicillin, erythromycin, and non-steroidal anti-inflammatory drugs have been reported as precipitating agents. There is an association with HLA-DRB1*01 in Caucasians and there appears to be a familial association.