Lid margin keratinization in Stevens-Johnson syndrome: Review of pathophysiology and histopathology.

Lid margin keratinization (LMK) is a chronic ocular sequela of Stevens-Johnson syndrome (SJS), which causes lid wiper epitheliopathy and progressive ocular surface damage. The exact etiopathogenesis of LMK, however, remains elusive. This review summarizes the potential pathophysiological mechanisms of LMK and describes its histopathological features. A literature search of articles discussing the pathophysiology of LMK in SJS was performed. The possible pathophysiologic mechanisms contributing to LMK, as identified on the literature review, included loss of the muco-cutaneous junction barrier leading to epidermalization, dyskeratosis involving the meibomian gland orifices, altered lid margin microbiome, and de novo squamous metaplasia of the marginal conjunctival epithelium. Based on these mechanisms, the possible sources of keratinized epithelium at the posterior lid margin in SJS could be the adjacent anterior eyelid skin, hyperkeratinized epithelium from the meibomian gland ductal orifices, or the inflamed marginal conjunctiva. The epithelial, sub-epithelial, and stromal changes seen in keratinized posterior lid margins in SJS patients undergoing mucous membrane grafting were also investigated. The findings revealed keratinizing squamous metaplasia of the posterior lid margin accompanied by subepithelial infiltration of helper T cells predominantly on the conjunctival side. The visible meibomian gland orifices had ductal hyperkeratinization and plugging. These findings support a role for inflammation in the pathogenesis of LMK in SJS. Future research can be directed at delineating the pathways that lead to LMK by studying the changes in the lid margin microbiome, and the molecular mechanisms regulating keratinization in the conjunctiva and the meibomian gland orifices in eyes affected by SJS.