MUC5AC and asthma: Mucin MUC4 was identified as aligand-activating receptor tyrosine kinase, which modulates the proliferationof airway epithelial cells in patients with asthma [25]; MUC19 is mainly expressed in the cells of submucousglands in the trachea and salivary glands; in patients with allergic rhinitisand chronic otitis media, this gene is expressed in the epithelium.