Genetics and pathogenesis of small-vessel vasculitis.

Small-vessel vasculitides are uncommon autoimmune diseases characterised by inflammation and necrosis of arterioles, capillaries and venules, frequently described as various (previously eponymous) clinical syndromes. Some are associated with vessel wall immune complex deposition, whereas others are pauci-immune but paradoxically often associated with circulating anti-neutrophil cytoplasmic antibodies (ANCA). Most is known about the pathogenesis of the pauci-immune ANCA-associated syndromes, which are gradually becoming better understood with regard to their genetic predisposition and the critical pathways mediating disease initiation, as well as their particular phenotypic features. Through better understanding of key cellular and molecular players, we have been able to develop novel biomarkers and treatment strategies, which should translate to improved diagnostics, treatment protocols and, ultimately, better patient outcomes. These conditions are treatable but not yet curable, although it is clear that patients may follow different disease courses, which for some include restoration of their pre-morbid immune status.