[Pathogenesis of large vessel vasculitides]

Large vessel vasculitides comprise two distinct entities, giant cell arteritis (GCA) and Takayasu arteritis (TAK). GCA is the most common vasculitis in central Europe, becoming manifested at an age over 50 years. In contrast, the much rarer TAK affects almost exclusively young adults and mostly women. Both vasculitides are granulomatous arteritides affecting mainly the aorta and its major arterial branches. GCA and TAK are associated with different major histocompatibility complex genes. Infections possibly play a role in the initiation of large vessel vasculitides. Activation of dendritic cells in the adventitia induces chemokine and cytokine-mediated recruitment and maturation of T‑helper (Th)1 and Th17 cells and macrophages producing cytokines, growth factors and matrix metalloproteinases. In GCA, CD4+ T‑helper cells and macrophages are predominantly found in the inflammatory infiltrate. In TAK, the infiltrate also contains cytotoxic CD8+ T‑cells and γδ T‑cells. This could indicate different antigenic triggers in GCA and TAK. Inflammatory infiltration with T‑cells and macrophages and activation of myofibroblasts and smooth muscular cells induce vascular remodeling with intimal hyperplasia and destruction of the media. Remodeling is histologically characterized by progressive arterial wall fibrosis, vascular stenosis and obstruction. In summary, GCA and TAK represent two different entities with a distinct human leukocyte antigen (HLA) and potentially etiopathogenetic background. Clinically, inflammation-related general symptoms and signs of ischemia are encountered, accompanied by increased levels of serological markers of inflammation.