IgG4 Expression in Patients with Eosinophilic Otitis Media

Objective: Eosinophilic otitis media (EOM) is an intractable middle ear disease recognized by an eosinophil enriched middle ear effusion and mucosa. Although precise pathogenesis of EOM remains unclear, it is characterized by type 2 inflammation. Since IgG4 is an IgG subclass induced by type 2 cytokines such as IL-4 and IL-13, we sought to characterize and compare local IgG4 expression in patients with and without EOM. Methods: Twelve patients with bilateral profound hearing loss, 9 of which underwent a cochlear implant surgery, were enrolled in this study (6 with EOM and 6 without EOM). The surgical specimens were harvested during surgery and were subjected to IgG4 immunostaining. Result: The middle ear mucosa showed the presence of a large number of IgG4-positive cells in patients with EOM, which was significantly higher than that in patients without EOM. Conclusion: Local IgG4 expression was observed in patients with EOM in comparison to those without EOM, suggesting that IgG4 contributes to EOM pathogenesis.