Narrative review: mucus plugging in chronic obstructive lung diseases and bronchiectasis

Background: Mucus plugging, complete intraluminal occlusions, is recurrently found in high-resolution computer tomography images in obstructive lung diseases and is increasingly recognized as clinically meaningful. Methods: A narrative review on pathophysiology, clinical consequences and treatment of mucus plugging. Results: In bronchiectasis, mucus hypersecretion and plug formation are associated with infections, such as Pseudomonas aeruginosa and non-tuberculosis mycobacteria and correlated to exacerbations. In chronic obstructive pulmonary disease, mucus plugging is related to greater airflow obstruction, worse health status, higher exacerbation risk, and increased mortality. In asthma, mucus plugging is associated with severe asthma and poorer outcomes. Multiple scoring systems for mucus plugs in chest computed tomography (CT) have been introduced but definitions are heterogenous limiting comparability. Conclusions: Mucus plugs are measurable markers of disease activity with prognostic relevance across obstructive airway diseases. Clinical adoption is hindered by non‑standardized CT scoring and limited plug‑targeted trials. New treatment options for mucus plugging e.g. biologics in asthma have been found successful, especially dupilumab. Azithromycin as a part of prevention of infections in obstructive lung diseases is effective. Future research is needed to standardize and validate CT-based mucus-plug scoring systems that could be brought into clinical medicine.