Characteristic differences in the lipid composition of middle ear effusions in adult and pediatric patients: phosphatidylethanolamine and phosphatidylserine levels.
Middle ear effusions (MEEs) from adult patients with otitis media with effusion are usually serous in nature, but those from pediatric patients younger than 8 years old are frequently mucous in consistency. MEEs contain substances secreted by the epithelial cells of the middle ear and eustachian tube to regulate surface tensions as well as those produced as the result of inflammation. Since the biochemical bases of serous and mucous MEEs have not been clearly established, we analyzed all lipid components of MEEs from seven children and seven adults by thin-layer and gas-liquid chromatography, and also compared them with those from sera. Although no significant difference in the lipid composition was observed between adult and pediatric sera, the relative concentration of phosphatidylethanolamine (PE) in the pediatric MEEs was 26.5%, while that in the adult MEEs was 9.2% and was significantly different. A similar high concentration of phosphatidylserine (PS) was also observed in the pediatric MEE. Since phospholipids are major components of surfactants secreted from the epithelial cells of the middle ear, significantly high concentrations of both PE and PS as charged phospholipids may be responsible in part for the mucoid characteristics seen in pediatric MEEs.