MUC5AC and chronic obstructive pulmonary disease: The results of some studies suggest that excessive mucin concentrations are positively correlated with the severity of COPD, increased mucin production in COPD and decreased lumen fluid, which have detrimental effects on airway health [39, 40]; the increase in MUC5B in the sputum of COPD patients is associated with a decrease in lung function [5].