Epidemiology of vasculitis - Lessons learnt from the differences in different geographical areas

The epidemiology of the vasculitides has been increasingly investigated over the past 30 years and we have now gathered significant knowledge about the occurrence of vasculitis in many populations. There is however still a lack of reliable data from the Indian subcontinent. For most types of vasculitis it is not known if differences in occurrence represent variation in genes, environment, or ascertainment. Giant cell arteritis is most common in populations of Northern Europe or Scandinavian origin and is rarer in the far East, whilst Takayasu arteritis is apparently commoner in Asia. The ANCA vasculitides have an overall occurrence that is similar in most populations, but in China and Japan microscopic polyangiitis is more common than granulomatosis with polyangiitis, whilst in Northern Europe the opposite occurs. Kawasaki disease is markedly more common in South East Asian populations than Caucasians. Behcet's disease is most common along the ancient silk route between the Mediterranean and China. Increasing genetic knowledge is beginning to explain these differences. Behcet's disease is strongly associated with HLA-B*51, Takayasu arteritis with HLA-B*52 and granulomatosis wit polyangiitis with the HLA-DPB1*0401 allele. Variations in allelic frequency might partially explain the global variation in occurrence.