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People who are carriers of cystic fibrosis (CF) can have children with CF if their partner is also a carrier. Multiple factors can impact the life expectancy of someone with cystic fibrosis, but people with CF live on average into their late 30s or 40s. It is important for people to know if they are a carrier of CF because some people use this information to make decisions around having children.
What is cystic fibrosis?
Cystic fibrosis is a condition that causes a buildup of thick, sticky mucus in the lungs and other organs. Everyone makes and needs mucus, but it is usually thin and gets cleared out of one’s system easily. People with CF have a hard time clearing this mucus out, and it ends up building up in places like the lungs and pancreas, which causes health problems.
Carriers of CF don’t have the condition, but they do have a chance of having a child with CF. This can happen if they have a child with someone who is also a carrier of CF.
The genetics behind CF explains this. Everyone has two copies of most every gene—one from each biological parent. A carrier has one copy of the CFTR gene with a DNA difference that can lead to CF and one copy of the CFTR gene that does not. To have CF, both copies need to have a DNA difference that leads to CF. This is why carriers do not usually have any CF symptoms.
At least ten million people in the U.S. are carriers of CF. And around 30,000 people have the disease. Every year about 1,000 people in the U.S. get diagnosed with this condition. About 1 in 30 are carriers. CF is much more common in people of European descent.
What are the symptoms of cystic fibrosis?
Most people go their whole life without knowing that they are a carrier of this disease.
For people with CF (those with two copies of the linked DNA differences), the symptoms can vary. Mucus buildup in the lungs can lead to shortness of breath, lung infections, coughing up of mucus, and breathing difficulties that get worse over time. Mucus buildup in the pancreas prevents it from doing its job to help get nutrition out of food. People with CF also often have liver problems.
While most people with the disease have cystic fibrosis symptoms in early childhood, some people with CF aren’t diagnosed with the disease until later in life. Only a physician or health care provider can diagnose CF.
Why is it important to learn about cystic fibrosis?
Today’s medical treatment helps people with CF live to their late 30s or 40s on average. Currently there is no cure, but new therapies and treatments are continually being developed.
When someone finds out they are a carrier of cystic fibrosis, it doesn’t mean they have CF, just that they have one copy of the gene. However, they could have a child with CF—if their child’s other biological parent is also a carrier. Each child of two carriers has a 1 in 4 chance of having CF.
If a couple finds out they are both carriers of cystic fibrosis, it might affect what they think about when deciding to have children. Some people may choose to not take action on this information in partnership with their healthcare provider or genetic counselor, while others may decide to not have children. And some may, after discussing their options with a healthcare provider, choose to use a variety of treatments to help lower their chances of having a child with CF.
How is cystic fibrosis passed down?
If a person is a carrier of CF, then most likely one of their parents passed it down to them. This means that at least one parent is probably a carrier too.
If a person is a carrier and the other biological parent is not, then each child has a 50% chance of being a carrier too. If both biological parents are carriers, then each child has a 50% chance of being a carrier and a 25% chance of having CF.
These numbers come from the genetics behind CF. As mentioned, everyone has two copies of most every gene—one from Mom and one from Dad. A carrier has one copy of the CFTR gene with a DNA difference that can lead to CF and one copy of the CFTR gene that does not. To have CF, both copies need to have a DNA difference that leads to CF. This is why carriers do not usually have any CF symptoms.
What does the test offered through AncestryHealth® look at?
The test offered through AncestryHealth® looks at one gene, CFTR, that is linked to cystic fibrosis. This is the only gene currently known to be associated with this condition.
What does this gene do? The CFTR gene gives instructions for making a protein. One of the many functions of this protein is that it helps your body keep the right balance of water and a chemical called chloride. When these levels are out of balance, a thick layer of mucus can build up in the lungs, pancreas, and other organs. This mucus can clog airways and other important ducts—which can lead to the symptoms of cystic fibrosis.
AncestryHealth® includes laboratory tests developed and performed by an independent CLIA-certified laboratory partner, and with oversight from an independent clinician network of board-certified physicians and genetic counselors. The test results are not diagnostic and do not determine your overall chance of developing a disease or health condition. The tests are not cleared or approved by the U.S. Food and Drug Administration. You should consult a healthcare provider before taking any action based on AncestryHealth® reports, including before making any treatment, dietary, or lifestyle changes. AncestryHealth® is not currently available in New York, New Jersey or Rhode Island.
- Cystic Fibrosis Foundation. Accessed August 13, 2019. www.cff.org/
- MacKenzie Todd, Gifford Alex H, Sabadosa Kathryn A., et al. Longevity of Patients With Cystic Fibrosis in 2000 to 2010 and Beyond: Survival Analysis of the Cystic Fibrosis Foundation Patient Registry. 2014;161(4): 233–241. www.ncbi.nlm.nih.gov/pmc/articles/PMC4687404.
- National Human Genome Research Institute. About Cystic Fibrosis. Accessed August 12, 2019. www.genome.gov/Genetic-Disorders/Cystic-Fibrosis
- National Institutes of Health (NIH). Genetics Home Reference. Cystic Fibrosis. ghr.nlm.nih.gov/condition/cystic-fibrosis