Cystic Fibrosis

Cystic fibrosis is an inherited condition in which glands produce excessively sticky mucus. The sticky material clogs the lungs, liver, pancreas, and intestines and makes it difficult to breathe and to digest food properly.

Rachel's Story

Rachel's parents were worried. They believed they provided all the proper care Rachel needed, just as they had for their older daughter when she was a baby, but Rachel failed to gain as much weight as other children her age, even though she seemed to have the appetite of a normal infant. Rachel also seemed to have more colds than other children had and a lot more colds than her older sister ever had. She coughed often and breathed with a wheezing sound. Then, around the time of her second birthday, Rachel developed pneumonia * .

Cystic fibrosis is a chronic disease in which the glands produce excessively sticky mucus that can clog the bronchial tubes in the lungs, making it difficult to breathe.

Cystic fibrosis is a chronic disease in which the glands produce excessively sticky mucus that can clog the bronchial tubes in the lungs, making it difficult to breathe.
Illustration by Frank Forney. © 2016 Cengage Learning®.

Rachel's failure to gain weight and her frequent respiratory infections led her doctor to suspect that Rachel had cystic fibrosis (SIS-tik fy-BRO-sis), which is usually known by its initials, CF. Tests confirmed the diagnosis.

CF is a hereditary disease that affects about 30,000 children and adults in the United States. It is one of the most common hereditary conditions. Especially affecting people of European ancestry, CF occurs in 1 of every 3,200 to 3,500 people. It affects other ethnic groups at a much lower frequency, with an estimated occurrence of about 1 in 9,500 people of Hispanic descent, 1 in 16,000 people of African American descent, and about 1 in 31,000 people of Asian descent. Nearly 1,000 new cases of CF are diagnosed each year in the United States, usually by the time children reach their second birthday.

What Is Cystic Fibrosis?

Cystic fibrosis (CF) is a chronic, hereditary disease that affects many of the body's organ systems. In CF, some of the thin, easy-flowing mucus * in the body's respiratory and digestive systems becomes thicker. Glands * produce mucus to do various tasks, such as lubricate the lungs, trap dust and bacteria that is inhaled through the nose, and protect the lining of the intestines from the acidic fluids that help digest food.

The glands in people with CF, however, produce sticky mucus that clogs the passageways in the lungs, which makes breathing difficult and leads to infections. The sticky mucus also blocks the easy flow of digestive acids and enzymes from the pancreas * and liver * to the intestines. Without adequate amounts of these digestive fluids in the intestines, people with CF cannot break down their food into the substances the body needs for nourishment.

What Causes Cystic Fibrosis?

CF is caused by a mutation in a gene * on chromosome 7. Chromosome 7 is one of 23 pairs of chromosomes that are part of each person's genetic makeup. The CF gene causes the production of a protein that lacks an important building block, or amino acid * . The missing amino acid is called phenylalanine (fen-il-AL-a-neen). Without that amino acid, the protein hinders the ability of mucus to obtain the proper amounts of water and salt from the body, and the mucus is unable to maintain its thin and easy-flowing texture. As a result, the mucus becomes dense and sticky and clogs the respiratory and digestive systems.

The obstructions in the lungs make breathing difficult and can increase the risk of infections. The problems in the digestive system prevent the body from getting all the nutrients it needs from food. It also means people with CF often have thicker, foul-smelling bowel movements, because fat in food cannot be broken down by digestive fluids and absorbed.

Cystic fibrosis is a chronic disease caused by a mutation in a gene located on chromosome 7.

Cystic fibrosis is a chronic disease caused by a mutation in a gene located on chromosome 7. If both parents carry the CF gene, there is a 50 percent chance that their child may carry the gene too, and a 25 percent chance that their child may have CF.
Illustration by Frank Forney. © 2016 Cengage Learning®.

A person may carry the CF gene on one of the two copies of chromosome 7 and not have any signs of CF. This person is called a carrier * . Parents can pass the CF gene to their offspring. If a person inherits the CF gene on both copies of chromosome 7, then that person develops CF. When parents are both carriers, such as Rachel's parents, their children have a one in four chance of having CF. Estimates are that 10 million Americans, or about 1 out of 30, carry the CF gene.

How Do Doctors Know Someone Has Cystic Fibrosis?

Descriptions of children with symptoms of cystic fibrosis appear as far back as the 1600s, but it was not until 1938 when CF was recognized as a separate disease. The symptoms of CF can sometimes be confused with pneumonia or asthma.


Cystic fibrosis affects each person differently. Many people with CF do not appear to be severely ill. In general, people with CF have some or all of the following symptoms:

In addition, people with CF may eat large amounts of food but still be hungry, because mucus blocks the ability of digestive enzymes *

Later, the pancreas may clog and fail to secrete the enzymes essential to normal digestion. The liver becomes clogged, which may lead to cirrhosis (si-RO-sis), a condition in which the liver becomes hardened and fails. Diabetes also develops frequently in people with CF as they get older.


Doctors may begin to suspect CF soon after a baby is born when the infant becomes ill with repeated respiratory infections, fails to gain weight despite a healthy appetite, and shows other symptoms of CF. In addition, about 10 percent of infants with CF have intestinal blockage due to thick mucus that is apparent at birth. Many of the symptoms of CF are common in people who do not have the disease, but tests are available to confirm that a person has CF.

A sweat test is a preferred method for diagnosing cystic fibrosis because it is relatively easy to perform and is accurate. The test determines the salt content of perspiration. Although sweat can seem salty in people who do not have CF, the level of salt in the perspiration of people with CF is higher. Besides the sweat test, medical professionals may use a more complicated test to look for the CF gene on both copies of chromosome 7.

A Morning Ritual for Rachel

After her doctor determined that Rachel had cystic fibrosis, her parents worried she would not be able to engage in the same activities her older sister or other children enjoy. As she grew, Rachel went to school, participated in sports, and performed many other everyday activities.

Most people with CF get treatment that involves helping them breathe more easily and digest food better, which makes day-to-day activities less difficult. Although their symptoms can range from mild to severe, many people with CF get treatments similar to those that Rachel receives. One of those treatments is chest physical therapy. Each morning, her parents vigorously thump her back and chest to help loosen the thick mucus in her lungs so she can cough it out. They learned the technique, called daily percussion therapy, from a physical therapist after Rachel was diagnosed with CF. Depending on the severity of the patient's condition, such therapy can take up to an hour. Sometimes, thumping is not enough, and the mucus must be extracted by suction.

Coughing is one of the main ways that people with CF can clear the mucus from their lungs, so Rachel coughs often at school. Because her teachers and the other students know Rachel has CF, they do not make a big deal about her coughing. Rachel keeps her own box of tissues on her desk, so she can cough the mucus into tissue and toss it into a nearby wastebasket.

Turning on the CF Gene

In 1989, scientists discovered the location of the CF gene. If they could replace the defective gene with a normal gene, then they would be able to cure the cells that produce the defective CF protein, in which case the mucus in the respiratory and digestive systems would be thin and easy flowing as opposed to thick and sticky.

In 1990, two teams of researchers were able to correct CF cells in lab dishes by adding normal copies of the gene. In the spring of 1993, a person with CF got the first experimental dose. In October 1993, scientists determined that gene treatment had repaired a damaged gene in a human patient. Numerous studies followed. Some have had very encouraging results, but no cure has been found.

Gene therapy is a complicated experimental process, and a particular hurdle has been finding a way to deliver the gene to the parts of the body where it can do its work. Perhaps gene therapy will never be able fix all of the defective genes, but it might cause enough of them to work properly to improve the quality of life for people with CF.

Boomer Fights Back

When two-year-old Gunnar Esiason was diagnosed with cystic fibrosis in 1993, his father, Norman Julius “Boomer” Esiason, decided to fight back. Boomer, who played quarterback for the National Football League's Cincinnati Bengals, New York Jets, and Arizona Cardinals and later became a television sports reporter, had been a fierce competitor for many years. Now, his greatest battle became the fight against CF.

The NFL star started the Boomer Esiason Foundation with the main goal of finding a cure for CF. The foundation supports basic research and clinical trials for new CF treatments.

At lunch and other times that she eats a meal or snacks, Rachel takes pills. The pills contain enzymes to help her digest food. Without them, the mucus in her digestive system prevents her from getting the nutrients she needs from food. Even with the enzyme pills, Rachel and others with CF often need to take vitamin supplements and eat a diet rich in nutrients to assure they get the proper nourishment.

Rachel and others with CF also take antibiotics to prevent or treat lung infections. Sometimes, the antibiotics are taken as pills or inhaled into the lungs using a device called a nebulizer. People with CF also sometimes take prescription medications that thin the mucus and help reduce lung inflammation, which makes breathing easier and helps reduce the number of lung infections.

DNase, which is short for recombinant human deoxyribonuclease, is one medication often used to treat CF. It does its job as a follow-up to the body's normal response to invading bacteria. The body fights bacterial infections with an army of white blood cells that destroy the bacteria. The blood cells die after they do their job. In people with CF, these dead white blood cells and bacteria serve to make the mucus thicker, basically turning its consistency from a fluid gel into semi-solid custard. DNase helps break down these dead white blood cells and bacteria, which allows the mucus to thin out again.

Living with Cystic Fibrosis

Once CF almost always caused death in childhood, but treatments in the last decades of the 20th century allowed many people with CF to live into adulthood. The symptoms can range from mild to severe, but eventually the recurring infections in the lungs begin to damage the lungs' ability to function. This complication is fatal for many people with CF. Lung transplantation has been performed on some patients who developed severe lung disease. The Cystic Fibrosis Foundation reports that nearly 2,800 people with CF have received lung transplants since 1990. In the last five years, about 150 to 200 people with CF have received lung transplants per year. Recent research has found that 67 percent of individuals with cystic fibrosis who receive a lung transplant live at least five years, and half live at least ten years after the transplant surgery.

According to the most recent Patient Registry data from the Cystic Fibrosis Foundation, the median predicted age of survival for people with CF is in the early 40s. With treatment, people with CF are able to perform many activities that other people do.

See also Asthma • Cirrhosis of the Liver • Genetic Diseases: Overview • Pneumonia


Books and Articles

Hebestreit, H., S. Kriemler, and T. Radtke. “Exercise For All Cystic Fibrosis Patients: Is the Evidence Strengthening?” Current Opinion in Pulmonary Medicine 21 no. 6 (November 2015): 591-595.

Miller, Petra. Cystic Fibrosis. New York: Cavendish Square Publishing, 2016.

Ong, T., and Ramsey, B.W. “Update in Cystic Fibrosis 2014.” American Journal of Respiratory and Critical Care Medicine 192, no. 6 (September 2015): 669-675.

Watson, Ronald, ed. Cystic Fibrosis. Amsterdam: Elsevier, 2015.

Yen, Elizabeth. Nutrition in Cystic Fibrosis. New York: Springer, 2015.


American Lung Association. “Cystic Fibrosis.” . (accessed March 5, 2016).

Cystic Fibrosis Foundation. “About Cystic Fibrosis.” (accessed March 5, 2016).

Mayo Clinic. “Cystic Fibrosis.” (accessed March 5, 2016).


Boomer Esiason Foundation. 483 10th Ave., Suite 300, New York, NY 10018. Telephone: 646-292-7930. Website: (accessed March 5, 2016).

Cystic Fibrosis Foundation. 6931 Arlington Rd., 2nd Floor, Bethesda, MD 20814. Telephone: 301-951-4422. Website: (accessed March 5, 2015).

* pneumonia (nu-MO-nyah) is inflammation of the lungs.

* liver is a large organ located beneath the ribs on the right side of the body. The liver performs numerous digestive and chemical functions essential for health.

* pancreas (PAN-kree-us) is a gland located behind the stomach that produces enzymes and hormones necessary for digestion and metabolism.

* glands are organs that produce substances such as hormones and chemicals that regulate body functions.

* mucus (MYOO-kus) is a thick, slippery substance that lines the insides of many body parts.

* genes (JEENS) are chemical structures composed of deoxyribonucleic acid (DNA) that help determine a person's body structure and physical characteristics. Inherited from a person's parents, genes are contained in the chromosomes found in the body's cells.

* amino acids (a-MEE-no) are the chief building blocks of proteins. In humans, certain amino acids are required to sustain life.

* carrier is a person who has in his body a bacterium or virus or gene for a disease that he can transmit to other people without getting sick himself.

* enzymes (EN-zimes) are proteins that help speed up a chemical reaction in a cell or organism.

Disclaimer:   This information is not a tool for self-diagnosis or a substitute for professional care.

(MLA 8th Edition)