Dropping acid: why is cystic fibrosis mucus abnormal?

Cystic fibrosis (CF) is associated with the production of viscous and adherent mucus in the airway. Indeed, in some countries, CF is still called “mucoviscidosis”. Mucus is a weak hydrogel exhibiting viscoelastic properties and these properties are important for normal function as they enable mucus to flow after secretion, to be effectively propelled by beating cilia (mucociliary clearance), and to provide a protective coating of the mucosal surfaces of our body that prevents dehydration and an exposure to external foreign substances and infectious agents. Mucus that is too thick or too thin can be difficult to transport by mucociliary clearance, and the production and accumulation of thick mucus in the airways eventually leads to mucostasis. The failure in function of mucus in airway clearance can lead to longer resident times of inhaled particulates including infectious agents, which results in chronic infection in the airway, lung damage and risk of death. Mucostasis and its associated problems are pathognomic features of the CF airway, and thus understanding the causes of abnormal mucus properties in CF is key to helping ameliorate the relentless progression of pulmonary disease. In cystic fibrosis, abnormal mucus viscosity and mucociliary clearance are due to decreased water and more solids, and not to changes in mucus pH