What are some of the conditions associated with Urticarial Vasculitis? What is the proposed pathogenesis?
UV has been described in association with SLE, Sjögren’s syndrome, lymphoma, hepatitis B and C, drug reactions, and IgM paraproteinemia (Schnitzler syndrome). The etiology is thought to be related to IC deposition. In patients with HUVS, the proposed pathogenesis is that IgG2 anti-C1q antibodies (C1q precipitins) bind to collagen-like regions of the C1q molecule, forming an IC that deposits in blood vessels causing activation of complement and other mediators, leading to vasculitic lesions. It has been proposed that the obstructive lung disease observed is a result of binding of anti-C1q antibodies to collagen-like regions of surfactant proteins in pulmonary alveoli. This, in combination with vasculitic lesions in pulmonary capillaries, causes lung injury, possibly due to influx of neutrophils and release of neutrophil elastase.
