The spectrum of lung muco-obstructive diseases that affect the airways, includes chronic obstructive pulmonary disease (COPD), Asthma, cystic fibrosis, primary ciliary dyskinesia (PCD), and non–cystic fibrosis bronchiectasis (NCFB), These diseases have the clinical features of cough, concentrated and thick sputum production, and episodic exacerbations that are often associated with a diagnosis of chronic bronchitis.
Human airway mucus is a hydrogel composed of approximately 98% water and 2% solids including high-molecular-weight mucin polymers. The two major synthesized and secreted respiratory mucins, MUC5B and MUC5AC, are physically very large proteins and a critical part of mucus.
In healthy persons, a well-hydrated mucus layer is transported rapidly (from the distal airways toward the trachea). In muco-obstructive diseases hyper-concentrated (dehydrated) mucus, failed mucus transport, and mucus adhesion to airway surfaces is observed. Mucus in the small airways cannot be cleared by cough and accumulates, forming airflow obstruction, infection, and inflammation (Bucher et al 2019).
MUC5 AC concentrations are significantly and abnormally raised in muco-obstructive diseases like COPD, Asthma, sub type of primary ciliary dyskinesia, and non–cystic fibrosis bronchiectasis — MUC5AC levels are consistent with its in the pathogenesis and lung function decline in muco-obstructive diseases.