Cystic fibrosis causes problems with how the lungs function


The CFTR* protein is found throughout the body, meaning that people with cystic fibrosis (CF) may experience a wide range of symptoms.


Inside the lungs is a network of tubes that divide into smaller and smaller tubes as you go deeper into the lungs. These tubes are called airways. The airways are lined with cilia, small hairs that sway back and forth to sweep mucus out of the airways.1


Airway of a person without CF

Normally, mucus in the lungs traps germs that can cause an infection. Then, the mucus is swept out of the lungs by the cilia. This mucus is coughed up and the germs are expelled.

For cilia to be able to do this the inside of the airways needs to be moist. This allows the cilia to move back and forth freely.2


*CFTR = Cystic fibrosis transmembrane conductance regulator


Airway of a person with CF

People with CF have reduced numbers of CFTR proteins or faulty CFTR proteins, which may result in the production of thick mucus.3 This makes it difficult for the cilia to move freely and sweep the mucus from the lungs. This causes mucus and germs to build up leading to CF symptoms such as:

  • Wheezing.4
  • Shortness of breath.4
  • A persistent cough that produces thick phlegm (sputum).4
  • Lung infections (from bacteria such as Pseudomonas aeruginosa, Burkholderia cepacia and Staphylococcus aureus).5
  • Bronchiectasis6 (damage to the airways that causes them to become wider and makes it harder to move air in and out as a person breathes and harder to clear mucus).

The build up can lead to pulmonary exacerbations (PEs). PEs are periods when symptoms get worse and may mean decreased lung function as well as more coughing and mucus, infection, and weight loss. In some cases PEs might need treating with antibiotics and a stay in hosptial.6



Airway of person without and with CF

Mucus is swept out of the lungs by cilia

Cilia are unable to sway freely and sweep mucus from the lungs

    1. Richardson, M. The physiology of mucus and sputum production in the respiratory system. Nursing Times 2003; 99(23).

    2. Derichs N. Targeting a genetic defect: cystic fibrosis transmembrane conductance regulator modulators in cystic fibrosis. European Respiratory Review 2013; 22(127): 58 - 65.

    3. Rowe S, et al. Mechanisms of Disease: Cystic Fibrosis. N Eng J Med 2005; 352: 1992 ̶2001.

    4. O'Sullivan B and Freedman S. Cystic fibrosis. Lancet 2009; 373(9678): 1891 ̶ 1904.

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