Cystic fibrosis (CF) is caused by mutations in the cystic fibrosis conductance transmembrane regulator (CFTR) gene, which provides instructions for making a protein of the same name. Dysfunction of the CFTR protein causes an abnormally thick mucus to build in the body’s organs, particularly the lungs, pancreas, liver, and intestine. In addition to being physically obstructive, this thick mucus can cause inflammation and tissue damage, leading to fibrosis (scarring).
The symptoms of CF begin to develop soon after birth. They can vary in severity significantly between patients and may ease or worsen with time. A patient may not experience all of the symptoms associated with CF, and some symptoms may not manifest until adolescence or adulthood.
Respiratory system symptoms
The thick, sticky mucus that characterizes CF can build in airways of the lungs, inhibiting airflow, causing lung inflammation, and leading to symptoms such as shortness of breath and a persistent cough.
The thick mucus also provides a fertile breeding ground for bacteria. As such, people with CF commonly experience recurrent lung infections, which can lead to more damaging lung inflammation. The key bacterial agent in CF lung infections is called Pseudomonas aeruginosa.
CF also may cause nasal and sinus inflammation, which are characterized by symptoms like congestion and a runny nose. Growths or swelling in the nose, called nasal polyps, also may develop. This can block the sinuses and lead to breathing difficulties.
Digestive system symptoms
The mucus produced by CF patients can also affect the digestive system. It can cause intestinal blockages, particularly in newborns, a condition called meconium ileus. These blockages may need to be removed with surgery.
Alterations in the digestive system caused by CF mucus may result in diarrhea, severe constipation, or foul-smelling and greasy stools. Severe constipation can lead to rectal prolapse, where the end of the large intestine, or rectum, protrudes outside of the anus due to frequent straining. This may require surgery to fix.
The mucus also can build up in the pancreas and liver, causing damage to these organs such as pancreatitis (pancreas inflammation), cirrhosis (liver scarring), or jaundice (yellowed skin caused by a buildup of a molecule that’s usually broken down by the liver).
Mucus in the pancreas may prevent the normal distribution of enzymes that are critical for digesting food, especially fats, setting the stage for malnutrition. Pancreas damage also helps lead to CF-related diabetes, which affects roughly half of adults with CF.
Reproductive system symptoms
Puberty can often be delayed in people with CF, and infertility is a common problem.
Males are often born without the vas deferens, a tube that delivers sperm from behind the testes, or this tube can become blocked by mucus. However, because sperm production is generally unaffected, it is possible for a man with CF to still have biological children with assistive reproductive technologies.
Females with CF will frequently experience irregular periods or ovulation. CF can make it hard to conceive, which may be exacerbated by complications such as thick mucus in the cervix. However, most women with CF are able to become pregnant if they choose.
People with CF are at increased risk of developing bone problems such as osteopenia or osteoporosis, when the bones are weaker than normal. The development of bone problems is influenced by many interconnected factors, including poor nutrition and frequent infections.
Clubbing, or deformities in the tips of the fingers and toes, may occur if the body is not getting enough oxygen.
The sweat of CF patients tends to have higher-than-usual salt content, owing to abnormal function of the CFTR gene, which normally helps to regulate the movement of salts in the body. Testing for levels of salt (specifically chloride) in sweat can be useful for diagnosing CF and monitoring CFTR protein function.
Last updated: Nov. 11, 2021
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