Although the inciting events in the pathogenesis of sympathetic ophthalmia and Vogt-Koyanagi-Harada (VKH) syndrome are different, these two forms of bilateral, granulomatous uveitis share several clinical, histopathological and immunohistochemical features, including their association with HLA types and in their in vitro T-cell response to retinal antigens. These clinical and immunopathological features indicate that there is an underlying T-cell mediated autoimmunity to uveal/retinal antigens in the development of these forms of uveitis. Both forms exhibit preservation of the choriocapillaris and retina despite extensive inflammatory cell infiltration in the choroid. Recent experimental studies suggest that this preservation of choriocapillaris could be the result of anti-inflammatory products secreted by the retinal pigment epithelium, including transforming growth factor-beta and a novel protein called retinal pigment epithelial protective protein that is known to suppress the phagocyte generation of superoxide. Such suppression of the oxidant release in the choroidal inflammation could help protect the uvea from necrotic change and preserve the choriocapillaris from inflammatory cell infiltration.
