Immunohistochemical study of epiretinal membranes in patients with uveitis

Background: The purpose of this study is to report two cases of idiopathic uveitis with secondary epiretinal membrane (ERM) formation in order to describe histologic and immunohistochemical features that may help distinguish uveitic from idiopathic ERMs. Methods: The study utilized a clinical case series and histopathological and immunohistochemical findings. Results: There was no identifiable etiology of inflammation in either case. Histology and immunohistochemistry demonstrated a mixture of abundant inflammatory cells, including lymphocytes, histiocytes, plasma cells, and occasional eosinophils, among a stromal matrix composed of glial elements and condensed vitreous, but no retinal pigment epithelium (RPE) was present. The relative proportions of the various inflammatory cell types were assessed with immunohistochemistry, and among the lymphocyte population, T cells predominated over B cells. In one of the cases, there was an abundance of histiocytes, consistent with granulomatous uveitis, which was later confirmed on histology of the enucleated globe. Conclusions: Idiopathic ERM formation is thought to be secondary to glial cell migration that may require some involvement of RPE cells. The absence of RPE and abundance of inflammatory cells may be used to identify ERMs as secondary to uveitis.