Immunohistochemical Differences Between Normal and Chronically Inflamed Conjunctiva: Diagnostic Features

There is widespread misinterpretation of normal conjunctival fibrinogen. In differentiating between normal conjunctiva and cicatrizing conjunctivitis, including ocular cicatricial pemphigoid, atopic keratoconjunctivitis, and lichen planus, it is important to properly evaluate and characterize the histologic appearance of the structures seen and not base a diagnosis on just the presence or absence of certain features. One feature of conjunctival histology prone to misinterpretation and misdiagnosis is the presence of subepithelial fibrinogen, particularly when the diagnosis of lichen planus is being considered. Although the presence of subepithelial fibrinogen in oral mucous membranes and in skin can be indicative of lichen planus, such is not the case for conjunctiva. An erroneous diagnosis of lichen planus based on the presence of conjunctival subepithelial fibrinogen can initiate prolonged treatment with topical steroids leading to avoidable, blinding, complication, and further, delay therapy for the real cause of the conjunctivitis. We conducted a cross sectional, controlled, blinded and prospective Institutional Review Board-approved study on the occurrence and pattern of fibrinogen at the epithelial basement membrane zone (BMZ) of normal and inflamed conjunctiva. Bulbar conjunctiva was obtained from 10 cases of undiagnosed chronic conjunctivitis of at least 6 months duration and 8 patients with normal conjunctiva. Immunofluorescent staining with antifibrinogen antibodies, periodic acid-schiff stain (PAS), and Giemsa staining were performed. BMZ fibrinogen was found in all cases. This layer was linear, smooth, and continuous in normal conjunctiva and 7 cases of chronic conjunctivitis. It was fragmented and lumpy in 1 case of ocular cicatricial pemphigoid (OCP) and showed spikes and spurs in 2 cases of lichen planus. BMZ fibrinogen is a normal component of the conjunctiva and its morphological features rather than its mere presence should be assessed as a diagnostic tool.