Introduction, epidemiology and classification of vasculitis.

Classification of the vasculitides has been traditionally based on vessel size. The American College of Rheumatology (ACR) criteria were developed in the 1980s and published in 1990 before the development of ANCA testing and modern imaging techniques such as MRI and PET scanning, and therefore, these criteria are not fit for use in 2010s. The Chapel Hill Consensus Conference provided a framework for defining various types of vasculitis. In the next two years, new classification criteria will be published from the DCVAS study, which will provide a modern system for the classification of vasculitis for clinical studies. The epidemiology of vasculitides is increasingly well studied; however, there remain gaps in our knowledge of the occurrence of vasculitis in many populations, especially from the third world or those with health care systems that do not permit ready collection of accurate epidemiological data. Giant cell arteritis presents in the elderly and those of Northern European ancestry; ANCA-associated vasculitis appears to have a consistent overall occurrence, but there are differences in the occurrence of MPO and PR3 vasculitis between populations. Kawasaki disease occurs most commonly in Asian populations, especially Japanese, and in those aged less than 5 years. It is currently the most common cause of acquired cardiac disease in those populations.