Compositional difference in middle ear effusion: mucous versus serous

Serous otitis media is usually responsive to medical treatment, whereas mucoid otitis media is not. The present study was undertaken to elucidate the compositional difference between serous and mucoid effusion and to investigate whether MUC5AC acts as a major mucin in the middle ear mucosa with mucoid otitis media.

This study involved a chemical analysis of middle ear effusion and immunostaining of the middle ear mucosa.

Middle ear effusion samples were collected from 27 patients with mucoid otitis media and 18 patients with serous otitis media. The levels of mucin, lysozyme, secretory immunoglobulin A, and interleukin-8 were measured by dot blotting or enzyme-linked immunosorbent assay. Periodic acid-Schiff and immunohistochemical staining with monoclonal anti-MUC5AC antibody were performed on the serial sections of middle ear mucosa with mucoid otitis media.

Mucoid effusions contained higher levels of mucin, lysozyme, secretory immunoglobulin A, and interleukin-8 than did serous effusions. Immunohistological study revealed that MUC5AC mucin was expressed in only a small portion of the goblet cells of middle ear mucosa with mucoid otitis media.

The study suggests that both serous secretions and mucin might make the middle ear effusion more viscous and that mucins other than MUC5AC might have a major role in the viscosity of middle ear effusion. Further study is necessary to identify the major mucins in the middle ear effusion of otitis media with effusion.