Classification Criteria, Epidemiology and Genetics; and Pathogenesis

Takayasu arteritis (TAK) is a granulomatous large-vessel vasculitis, predominantly affecting the aorta and/or its major branches. Younger age is often used to distinguish it from patients with another form of large-vessel vasculitis, giant cell arteritis, but older age at onset has been well recognized. The incidence and prevalence of TAK varies by geographic region with the highest estimated prevalence in Japan at 40 per million. The strongest genetic susceptibility is with the major histocompatibility complex (MHC) Class I allele HLA-B52. The etiology of TAK is unknown and the pathogenesis is poorly understood. Histopathology of affected vessels show mixed inflammatory infiltrate comprising of macrophages with variable amounts of T- and B-lymphocytes and plasma cells. Cell-mediated autoimmunity appears to play a major role in TAK with recent studies demonstrating the importance of T-helper subsets Th1 and Th17.