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Cystic fibrosis is a genetic disease. That means people inherit it from their parents through genes (or DNA), which also determine a lot of other characteristics, including height, hair color and eye color. Genes, found in the nucleus of all the body’s cells, control cell function by serving as the blueprint for the production of proteins.

To have cystic fibrosis, a person must inherit two copies of the defective CF gene — one copy from each parent. If both parents are carriers of the CF gene (i.e., they each have one copy of the defective gene), their child will have a 25% chance of inheriting both defective copies and having cystic fibrosis, a 50% chance of inheriting one defective copy and being a carrier, and a 25% chance of not having CF or carrying the gene.

Approximately 30,000 people in the United States have cystic fibrosis. An additional 10 million more — or about one in every 31 Americans — are carriers of the defective CF gene, but do not have the disease. The disease is most common in Caucasians, but it can affect all races..

The severity of cystic fibrosis symptoms is different from person to person. The most common symptoms are:

  Very salty-tasting skin
  Persistent coughing that usually produces phlegm
  Frequent lung infections
  Wheezing or shortness of breath
  Poor growth/weight gain in spite of a good appetite
  Frequent greasy, bulky stools or difficulty in bowel movements
  Small, fleshy growths in the nose called nasal polyps

New research shows that the severity of CF symptoms is partly based on the types of CF gene mutations, or defects. Scientists have found more than 1,500 different mutations of the CF gene.

How and why does CF affect the body?

Scientists have many different ideas about what goes wrong in the lungs of a person with cystic fibrosis, but it all begins with defective CF genes.

Normally, the healthy CF gene makes a protein — known as CFTR (Cystic Fibrosis conductance Transmembrane Regulator) — that is found in the cells that line various organs, like the lungs and the pancreas. This protein controls the movement of electrically charged particles, like chloride and sodium (components of salt) in and out of these cells.

When the protein is defective, as in cystic fibrosis, the salt balance in the body is disturbed. Because there is too little salt and water on the outside of the cells, the thin layer of mucus that helps keep the lungs free of germs becomes very thick and difficult to move. And because it is so hard to cough out, this mucus will clog the airways and lead to infections that damage lungs.

In addition, the mucus that builds up in people with CF can block tubes, or ducts, in the digestive system. The pancreatic duct is especially vulnerable; when it is blocked, enzymes that help digest food cannot reach the intestines, and the body cannot properly absorb nutrition from food. The resulting malnutrition compromises the body’s immune system and can lead to diarrhea, poor growth and weight loss.

The reproductive system is also affected by CF, which can cause infertility, particularly in men. At least 97 percent of men with CF are infertile but are not sterile; they can have children with assisted reproductive techniques. Some women also have fertility difficulties due to thickened cervical mucus or malnutrition.


How can you know for sure if you or your child has cystic fibrosis? If someone in your family has the disease, could you pass it down to your children?

There are several ways to help answer these important questions.

Genetic Carrier Testing — More than 10 million Americans are symptomless carriers of the defective CF gene. This test can help detect carriers, who could pass CF onto their children. To have cystic fibrosis, a child must inherit one copy of the defective CF gene from each parent.

Each time two carriers of the CF gene have a child, the chances are:

  25% the child will have CF;
  50% the child will carry the CF gene but not have CF; and
  25% the child will not carry the gene and not have CF.

Newborn Screening — Newborns screened for cystic fibrosis can benefit from early diagnosis and treatment, which can:

  improve growth;
  improve lung function;
  reduce hospital stays
  add years to life.

While newborn screening is not a definitive diagnostic test for cystic fibrosis, it may lead to tests that can rule out or confirm a CF diagnosis.

Sweat Test — If a person exhibits symptoms of CF, a doctor may order a sweat test. This simple, painless test is the best way to diagnose CF. It measures the concentration of salt in a person’s sweat. A high salt level indicates CF.

Sweat tests should be done at an accredited CF care center, where strict guidelines help ensure accurate results.

Staying healthy and maintaining optimal lung function requires people with cystic fibrosis to follow a regular treatment routine. The therapies for CF include airway clearance techniques, a variety of medications and good nutrition. If and when a person with CF develops severe lung disease, they may discuss the option of lung transplantation with their CF care team.

Scientists and researchers are working every day to find a cure for cystic fibrosis and also to develop treatments that greatly improve the quality of life for CF patients. Each day since the cystic fibrosis gene was discovered in 1989, the pace of CF research has greatly accelerated, and scientists continue to find ways to help those who live with the disease.

Drug Discovery Pipeline

The Cystic Fibrosis Foundation has built a dynamic “pipeline” for the development of more new potential CF therapies than ever before. To treat a complex disease like cystic fibrosis, therapies must target problems in the airways and the digestive system. In the CF pipeline, there are always promising new therapies designed to rectify the faulty gene and/or its faulty protein product – the root cause of the disease. Visit the Cystic Fibrosis Foundation drug development pipeline page.

Clinical Trials

Clinical trials are research studies organized to answer specific questions about new therapies or new ways of using known treatments. Clinical trials (also called medical research and research studies) are used to determine whether new drugs or treatments are both safe and effective. The Cystic Fibrosis Foundation maintains a database of ongoing clinical trials, with information about participation requirements, findings, etc.