Pharyngeal Deposits Comprising Salivary Mucin in Tube-fed Elderly Patients: MUC2 and MUC7 Immunoreactivity

Several investigators have reported that oral membranous and pharyngeal viscous deposits developed in bedridden elderly persons requiring nursing care without oral intake. Therefore, this study aimed to clarify the origin of viscous deposits on the pharyngeal mucosa based on characteristics of salivary and tracheal secretory mucin. The participants were 35 elderly people who required nursing care. All 46 collected specimens, including 30 intraoral and 16 pharyngeal specimens, were stained against specific mucins secreted from the respiratory tract and saliva gland using antibodies anti-MUC2 and anti-MUC7, respectively. Out of 35 participants, the intraoral membranous deposits and deposits on the pharyngeal mucosa developed in 17 (48.6%) and 10 persons (28.6%), respectively. The pharyngeal deposits developed in 58.8% of participants who developed intraoral deposits. All pathological specimens shared microscopic findings of various combinations of eosinophilic lamellar structure and a pale-basophilic amorphous substance. Immunohistochemically, both the 30 oral and the 16 pharyngeal specimens obtained from 17 participants were consistently positive for MUC7 but negative for MUC2. In conclusion, we clarified that the mucoid component of both oral and pharyngeal deposits comprised MUC7 salivary mucin, which revealed that both deposits originated from the oral cavity. This result strongly suggests that oral care is intimately related to oral and pharyngeal conditions.