Cystic Fibrosis


What is cystic fibrosis (CF)?

Cystic fibrosis (CF) is a genetic (inherited) disease that causes sticky, thick mucus to build up in organs, including the lungs and the pancreas.

In a healthy person, mucus that lines organs and body cavities, such as the lungs and the nose, is slippery and watery. In people who have CF, thick mucus clogs the airways and makes it difficult to breathe. Blocking the ducts in the pancreas causes problems with digesting food, so babies and children who have CF may not be able to absorb enough nutrients from food.

Other organs that are affected by CF are the liver, sinuses, intestines and sex organs. CF is a chronic (long-lasting) and progressive (getting worse over time) condition.

How common is cystic fibrosis (CF)?

Among white children in the United States, the rate of CF cases is one in 3,500 newborns. CF affects about one in 17,000 black newborns and one in 31,000 newborns of Asian descent.

Symptoms and Causes

What causes cystic fibrosis (CF)?

CF is passed through the CFTR genes. People who have CF inherit two faulty genes, one from each parent. The parents do not have to have CF; in fact, many families do not have a family history of CF. In this case, the person with the faulty gene is called the carrier. About one in 31 people in the United States is a carrier who is free of CF symptoms.

What are the symptoms of cystic fibrosis (CF)?

Children who have CF have the following symptoms:

  • Failure to thrive (inability to gain weight despite having a good appetite and taking in enough calories)
  • Loose or oily stools
  • Trouble breathing
  • Recurrent wheezing
  • Frequent lung infections (recurrent pneumonia or bronchitis)
  • Recurrent sinus infections
  • A nagging cough
  • Slow growth

Diagnosis and Tests

How is cystic fibrosis (CF) diagnosed?

In most cases, CF is diagnosed during childhood. Doctors diagnose CF with a thorough evaluation and by using different tests. These include:

  • Newborn screening: A healthcare provider takes a few drops of blood from a heel prick, usually while the newborn is in the hospital, and places the drops on a special card called a Guthrie card. Tests at a laboratory can diagnose conditions, including CF. Every state in the United States requires the testing of newborns at birth as well as a few weeks later.
  • Sweat test: The sweat test measures the amount of chloride in the body’s sweat, which is higher in people who have CF. In the test, a healthcare provider spreads a chemical called pilocarpine on the patient’s skin, then applies a small amount of electric stimulation to encourage the sweat glands to produce sweat. The provider then collects the sweat in a plastic coil or on a piece of filter paper or gauze. People of any age can have a sweat test. It is not painful and does not use a needle. This is the most conclusive test for CF.
  • Genetic tests: These are performed using a blood sample that is tested for the faulty genes that cause CF.
  • Chest X-rays: X-rays of the chest are used to support or confirm CF if a healthcare provider suspects that a person has the disease. Other forms of testing need to be used to confirm the presence of CF.
  • Sinus X-rays: As with chest X-rays, sinus X-rays can confirm CF in patients who show certain symptoms. Other forms of testing are used along with sinus X-rays.
  • Lung function tests: The most common lung function test uses a device called a spirometer. The patient breathes in completely, then empties the inhaled breath into the mouthpiece of the spirometer.
  • Sputum culture: A healthcare provider takes a sample of a patient's sputum (spit) and tests it for bacteria. Certain bacteria, such as pseudomonas, are most commonly found in people who have CF.

Management and Treatment

How is cystic fibrosis (CF) treated?

In most cases, the patient visits a CF care center four times a year. The caregivers at the center:

  • Show the patient techniques for clearing mucus from the airways, which will aid in keeping his or her lungs healthier.
  • Detect complications of CF and treat these in a timely manner.
  • Offer medications and information about nutrition therapy and physical fitness.

In the last few years, a number of medications called CFTR modulators have been developed to improve functioning of the CFTR protein. These medications are now widely used. Their use depends on which CFTR genes people have, but many individuals who have CF can use these new medications.

Why is a high calorie, high fat diet needed for people with cystic fibrosis (CF)?

Children and adults with cystic fibrosis (CF) have nutritional needs that are different than what would normally be recommended for children and adults without cystic fibrosis. Children and adults may need one and one-half to two times the number of calories as people without CF. More calories are needed because it takes more energy for a person with CF to breathe, fight lung infections and maintain a strong body than a person without CF.

More calories and fats are also needed because the CF prevents the pancreas’s digestive enzymes from fully working as they should, resulting in nutrients and fats from foods not being fully absorbed by the intestines. Although the enzyme capsules that are taken before all meals and snacks helps digest fats, proteins, and starches, a certain amount of nutrients and fats don’t get absorbed. If not enough fats are being absorbed, then fat-soluable vitamins aren’t being fully absorbed and these vitamins are needed to protect the lungs.

It’s also important to emphasize that maintaining a higher than normal weight is very important from early childhood onward. Researchers have shown that young people with CF who maintain a higher weight grow faster and taller up to puberty and again grow taller when they hit their growth spurt at puberty. Young people with CF who started life at a lower weight did not grow as many inches, started puberty at a later age and never got that same puberty growth spurt. Reaching your full genetic potential – getting as tall as possible with lungs as large as possible – is another reason why higher than normal weight in young people with CF is so important.

Salt (sodium) intake. Another common misbelief is that salt (sodium) is unhealthy for all people. This is not the case for children and adults with CF. People with CF lose a lot of salt in their sweat. Although there is not a set standard, doctors generally advise people with CF to eat salty foods especially during hot, humid weather and when they exercise. Also, to add salt to meals and snacks as desired. Ask your doctor or dietician about the amount of salt you need each day.

What are the complications of cystic fibrosis (CF)?

The complications of CF include the following:

  • Adults who have CF can have problems with breathing, digestion, and the reproductive organs.
  • The thick mucus present in people who have CF can hold bacteria, which can cause infection to occur more often.
  • People who have CF have a higher risk of developing diabetes or the bone-thinning conditions osteopenia and osteoporosis.
  • Men who have CF are not able to father children without the aid of alternative reproductive technology. Women who have CF can have a decrease in fertility (the ability to have children) and complications in pregnancy.

Outlook / Prognosis

What is the prognosis (outlook) for patients who have cystic fibrosis (CF)?

There is no cure for CF and it cannot be prevented. However, new treatment methods help children who have CF live well into adulthood and have a better quality of life. Advances in the treatment of CF have increased the expected age of a patient’s survival, from the mid-teens in the 1970s to more than 36 years old currently.

Therapies are most helpful when CF is diagnosed early, which is why newborn screening is so important. These therapies include treating infections, helping to prevent weight loss, and being seen frequently by a CF specialist. These young patients can thus begin receiving the earliest, most up-to-date and aggressive therapy. The addition of CFTR modulator therapy at a young age seems to be very beneficial and may improve long-term health.

Last reviewed by a Cleveland Clinic medical professional on 06/13/2019.


  • Cystic Fibrosis Foundation. . Accessed 6/10/2019.About Cystic Fibrosis (
  • National Heart, Lung, and Blood Institute. . Accessed 6/10/2019.Cystic Fibrosis (
  • U.S. National Library of Medicine/Genetics Home Reference. . Accessed 6/10/2019.Cystic Fibrosis (
  • Cystic Fibrosis Foundation. Accessed 6/10/2019.Nutritional basics. (
  • Cystic Fibrosis Foundation. Accessed 6/10/2019.Minerals. (

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