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CF Source

The Symptoms of CF

Select different parts of the body to explore how they're affected by CF.


Airways in the lungs

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

Airways in the lungs
Airways in the lungs

Watch this video to see what happens in the lungs of a person with CF.

Airways of a person without CF

Normally, mucus in the lungs traps germs and particles. Then the mucus is swept out of the lungs by the cilia. The mucus can then be coughed up, and the germs and particles are expelled.

For cilia to be able to sweep mucus out of the lungs, the inside of the airways needs to be moist. This allows the cilia to sway back and forth freely.

Airway of Person Without CF
Airway of Person Without CF

Airways of a person with CF

Because water and salt can't flow freely into or out of cells, the inside of the airways of a person with CF is not as moist as the inside of the airways of a person who does not have CF. This makes it difficult for the cilia to sway freely and sweep the mucus from the lungs.

This causes mucus and germs to build up in the lungs. Germs (which can lead to infection) can then build up in the lungs. This causes inflammation and scarring that can lead to more obstruction. This can lead to pulmonary exacerbations. Pulmonary exacerbations are periods when symptoms get worse. This can mean decreased lung function, as well as more coughing and mucus, infection, and weight loss. Pulmonary exacerbations can also lead to the need for intravenous (IV) or oral antibiotics and hospital stays.

The repeated cycle of mucus buildup, infection, and inflammation can cause damage to the airways. This includes a condition called bronchiectasis. This is a permanent reshaping of the airways, which causes them to become loose and scarred. Bronchiectasis can make it harder to clear mucus from the lungs. It also makes it harder for the airway to move air in and out as a person breathes.

Airway of Person With CF
Airway of Person With CF

This thick mucus may also cause other CF symptoms such as:

  • Wheezing
  • Shortness of breath
  • A persistent cough that produces thick phlegm (sputum)

Learn how CF progresses in the lungs over time

Digestive System

Flow of pancreatic enzymes

The pancreas makes digestive enzymes that the body uses to break down food. These enzymes are contained in pancreatic juices. These juices flow through pancreatic ducts to the small intestine. In a person with CF, the pancreatic juices are thick. They block the ducts. This makes it harder for the digestive enzymes to reach the small intestine where they do their job.

Without these enzymes, the body has trouble breaking down food and absorbing vital nutrients. This leads to:

  • Poor growth and slow weight gain, even if a lot of food is eaten
  • Frequent, greasy, and bulky stools

Flow of Enzymes
Flow of Enzymes

Watch this video to see what happens in the digestive system of someone with CF.

Poor nutrition

Poor nutrition, or malnutrition, occurs in a person with CF because many of the nutrients from food are not absorbed in the body. Because of this, a person with CF may need up to twice the amount of calories per day compared with people who are the same age and weight but don’t have CF.

Children, including those with CF, should be steadily growing and gaining weight. When this is not the case for a child with CF, it could be a sign of poor nutrition.

For an adult with CF, weight loss is also usually a sign of poor nutrition.

There are various reasons that a person with CF may experience weight loss:

  • A reduced flow of pancreatic enzymes into the small intestine may make it hard to get nutrients from food
  • During pulmonary exacerbations, the body may burn a lot of calories fighting off infection
  • People who also have cystic fibrosis–related diabetes (CFRD) may not be able to use the sugar from the foods they eat

Assessing weight and growth

Body mass index (BMI) is an important measure used to evaluate growth and nutrition in a person with CF. BMI measures a person’s weight in relation to their height. It is a better way to measure proper nutrition and detect malnutrition than just weight alone.

For children with CF ages 2-20 years:

  • BMI percentile is recommended to be at or above the 50th percentile. This means half of the children of the same age and gender are larger and half are smaller

For adults with CF:

  • Recommended BMI goal is 22 kg/m2 for females and 23 kg/m2 for males

Proper nutrition is important not only for growth, but it has also been shown to be associated with better lung function in people with CF.

Know your BMI
If you don't know what your BMI is, or what range it should be in, speak with your healthcare provider for more information.

Gastroesophageal reflux disease (GERD)

People with CF may be more likely to have gastroesophageal reflux disease, or GERD. GERD is an increase of acid leaking from the stomach back into the esophagus, the tube that leads from the mouth to the stomach. GERD may cause pain and lead to swelling. In severe cases, it may lead to breathing problems. In addition, a lot of coughing may also force acid from the stomach into the esophagus.

Learn how CF progresses in the digestive system over time

Other Parts of the Body

People with CF may experience symptoms in other parts of their bodies besides the lungs and the digestive system. Below is a list of some of those symptoms.

Nasal polyps

People with CF tend to have more nasal polyps, or fleshy growths, inside their noses. It is not clear how CF causes polyps. Nasal polyps can lead to postnasal drip, or mucus running down the back of the throat. Some of this mucus may end up in the lungs.


Sinusitis may occur in people with CF. Sinusitis is inflammation or swelling in the sinus cavity. It may result from thick, sticky mucus blocking the sinuses. This blockage may lead to sinus infections.

Salt loss

Normally, the CFTR protein reabsorbs the chloride of the salt in sweat before it reaches the skin surface. In people with CF, the CFTR protein is not reabsorbing the chloride. So they usually have much higher sweat chloride levels, and therefore more salt in their sweat.

Over 99% of people with CF have abnormally high sweat chloride levels. They have 2 to 5 times more salt in their sweat than people who don’t have CF. That’s why when CF is suspected, sweat is tested for its sweat chloride level to help diagnose CF.

People with CF also lose more salt than normal in their sweat. When they sweat more due to hot weather, exercise, or fever, more salt is lost. Losing too much salt can lead to dehydration and heatstroke. It’s recommended for people with CF to have a high-salt diet to replace these losses.

Some symptoms of losing too much salt are:
  • Tiredness
  • Weakness
  • Vomiting
  • Fever
  • Muscle cramps
  • Stomach ache

Learn how CF progresses in other parts of the body over time