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CF Below
the Surface

Cystic fibrosis (CF) feels a little different for everyone. But it all starts with a problem within the cells. Mutations found on both copies of a specific gene cause proteins throughout the body to be made incorrectly. This results in a buildup of thick, sticky mucus in the lungs and beyond, leading to frequent inflammation and infections that can cause damage, even before it can be felt.

Living with CF

Cause of CF

CF starts small—within the cells

Genes, which tell our bodies what our physical features will look like, are also the cause of certain diseases. A specific gene is responsible for CF. It’s called the cystic fibrosis transmembrane conductance regulator (CFTR) gene, and everyone has 2 CFTR genes—not just people with CF. This gene contains the instructions for producing CFTR proteins, which do an important job on the surface of certain cells throughout the body. But when someone has CF, a change in both copies of this gene (called a mutation) results in CFTR proteins that aren't able to do their job. Because of this, mucus, which is a slippery substance lining many different organs, gets too thick, causing infections and damage.

CF Fact or Fiction CF Fiction CF Fact or Fiction CF Fiction

If someone has 
a mutation in one of their CFTR genes, it means they’ll have CF.

Here's the truth:
In order for someone to have CF, they must have a mutation in both of their CFTR genes.


CFTR Protein Defects

Defects vary by mutation

Over 2,000 mutations in the CFTR gene have been discovered.

About 281 mutations 

cause the range of different protein defects 

that result in CF.

Watch the videos below to learn about these CFTR defects

All the CFTR mutations 
that cause CF result in thick, sticky mucus

There's one thing that remains the same across CF-causing CFTR protein defects—they all cause mucus in different parts of the body to thicken. Even if someone with CF doesn’t feel it, this mucus can cause damage from an early age. And although most people think of the lungs when they think of CF, other parts of the body are affected as well.

Impact on the Lungs Impact on the Lungs

Buildup of mucus causes infections and lung damage

Thick, sticky mucus found in the airways of the lungs of someone with CF may cause symptoms such as wheezing, shortness of breath, and a persistent, phlegmy cough. This mucus builds up and can’t be cleared from the airways easily. The germs found in this mucus build up as well, causing infection, inflammation, and scarring.

The buildup of mucus and germs also leads to pulmonary exacerbations. Most people with CF are familiar with pulmonary exacerbations as periods of time when symptoms get more severe and may require intravenous (IV) antibiotics or a hospital visit. The lung damage caused by pulmonary exacerbations may be permanent.

Digestive System Impact

Thicker digestive juices damage organs

While CF is often thought of as a problem with the lungs, it also causes significant problems in the digestive system, particularly in the pancreas and liver.

The pancreas

Thick juices block the ducts within the pancreas, an organ in the digestive system that helps break down food. This blockage 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 nutrients. Not having these enzymes can also lead to:

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

The liver

The liver is another part of the digestive system affected by this mucus. Inside the liver are tubes called ducts that are meant to drain it of bile. In people with CF, bile is thicker. As a result, the bile ducts can become blocked, leading to irritation or inflammation in the liver.

The intestines

Some people with CF may also experience distal intestinal obstruction syndrome (DIOS), a complete or incomplete blockage of the intestines due to thicker digestive juices.

Other Effects of CF

Thicker mucus also causes problems in other organs


CF can also cause sinusitis, which is inflammation or swelling in the sinus cavity. Mucus blocks the sinuses, leading to sinus infections and potentially lung function decline.

Infertility in women

For a woman who has CF, mucus in her reproductive system may make it difficult for sperm to travel to the uterus. This may make fertilization of a woman's eggs difficult.

CF Fact or Fiction CF Fiction CF Fact or Fiction CF Fiction

CF is only a
disease of the

Here's the truth:
CF affects
many different
systems of 

the body.


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