Cystic fibrosis, or CF, is a genetic disease characterized by the buildup of abnormally sticky and thick mucus. This mucus builds up in various organs, including the lungs, pancreas, liver, and intestines, and causes damage.
CF is caused by mutations in the gene cystic fibrosis transmembrane conductance regulator (CFTR). This gene provides cells with instructions for making a protein, also called CFTR, that normally functions like a “gate” on the surface of certain cells, regulating the flow of water and salts in and out.
In CF, mutations cause the CFTR protein to be dysfunctional or missing. There are more than 2,000 different types of mutations, each with specific effects on the protein — but in all cases, the protein doesn’t work correctly. The end result is that cells cannot properly regulate the flow of salt and water, leading to the production of the thick and sticky mucus. Normal mucus is about 97% water, which is important because mucus needs to be wet and slippery to keep organs protected and lubricated.
The disease is inherited in an autosomal recessive pattern, which means that a person will develop CF only if they have two mutated copies of the CFTR gene (one inherited from each biological parent). Someone with only one copy of the mutated gene won’t develop CF, but may pass the disease-causing mutation to their biological children.
A variety of tools are available to help diagnose CF. Genetic testing can identify disease-causing mutations in the CFTR gene, and CT scans can be used to image mucus in the body and monitor lung damage.
The sweat test and nasal potential difference test can detect evidence of dysfunction in the CFTR protein by assessing abnormalities in the amount of salt in sweat or the airways.
In the U.S., Canada, Australia, and most of Europe, newborn screening for CF is conducted in infants within days of birth. This often involves genetic testing and/or the IRT test.
Most of the symptoms of CF are caused by the accumulation of thick mucus in the body’s organs. In the lungs, mucus can clog the airways, leading to difficulty breathing and inflammation. Mucus in the lungs is also a fertile environment for the growth of disease-causing bacteria such as Pseudomonas aeruginosa. People with CF may experience chronic lung infections or pneumonia.
The buildup of mucus in the pancreas can block the release of enzymes needed to digest food, especially fats, leading to problems with digestion and inadequate nutrition. Nearly half of adults with CF will develop diabetes related to the disease. Inadequate nutrition is one of the main contributing factors to bone problems, which are estimated to affect one in three CF patients.
People with CF often go through puberty at a later age than their peers, and the disease can cause infertility and other reproductive issues.
Various medications are available to ease symptoms, extend longevity, and improve quality of life for people with CF. For example, antibiotics can be used to combat lung infections caused by Pseudomonas and other bacteria.
Inhaled therapies to ease lung symptoms are available, such as bronchodilators (which widen the air passages in the lungs), mucolytics — which help break up mucus — and anti-inflammatory corticosteroids.
CFTR modulators are a recently developed class of medicines that work by correcting the defect of the CFTR protein caused by particular mutations.
Some non-pharmaceutical therapies may also be used to ease symptoms and improve life quality for people with CF. For instance, oxygen therapy can help ensure patients get enough oxygen, especially while they sleep. Physiotherapy, high-frequency chest wall oscillation, and positive expiratory pressure all can help patients clear mucus from the lungs.
Last updated: Sept. 29, 2021
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