ConditionLungs & breathing
Cystic Fibrosis
Cystic fibrosis (CF) is an inherited disease caused by faulty copies of the CFTR gene, which controls the movement of salt and water across cell surfaces. The result is thick, sticky mucus that clogs the lungs, pancreas and other organs, causing repeated chest infections, poor digestion and slow growth. It is usually found by newborn screening and confirmed with a sweat test. New CFTR modulator medicines treat the underlying defect in most people with CF and have transformed life expectancy.
Also called: CF, mucoviscidosis
At a glance
- Cause
- Two faulty copies of the CFTR gene, one from each parent (autosomal recessive).
- How common
- Around 40,000 people in the US. Most common in people of Northern European descent, but occurs in all ancestries.
- Main effects
- Thick mucus in the lungs (infections, bronchiectasis), pancreas (poor digestion, diabetes), sinuses, liver, gut and reproductive tract.
- Diagnosis
- Newborn screening blood spot, confirmed by a sweat chloride test and genetic testing.
- Treatment
- CFTR modulators (such as elexacaftor/tezacaftor/ivacaftor), airway clearance, inhaled medicines, antibiotics, enzymes and nutrition.
When to get help
Call 911 or go to the ER
- Severe breathlessness, blue lips or confusion
- Coughing up a large amount of blood (more than a few spoonfuls)
- Sudden chest pain with breathlessness (possible collapsed lung)
- Severe abdominal pain with a swollen belly and vomiting (possible bowel blockage)
See a doctor within a day or two
- Increased cough, more or darker sputum, fever, or a drop in lung function (a pulmonary exacerbation)
- Signs of dehydration or heat exhaustion, especially in hot weather, because people with CF lose extra salt in sweat
- Persistent high blood sugar symptoms: thirst, urination and weight loss
Book a routine appointment
- A child with a persistent cough, frequent chest infections, greasy stools, poor weight gain or salty-tasting skin
- Planning a pregnancy as a carrier or with CF
- Regular CF clinic reviews every 3 months
What causes cystic fibrosis
The CFTR protein acts as a channel that moves chloride across cell membranes, drawing water with it to keep mucus thin. In CF, the protein is missing or does not work, so secretions become thick and sticky.
CF is autosomal recessive. A person must inherit two faulty CFTR genes, one from each parent. Carriers have one faulty copy and are healthy. When two carriers have a child, each pregnancy has a:
- 25% chance of CF
- 50% chance of being a carrier
- 25% chance of neither
About 1 in 30 white Americans carries a CF mutation, with lower carrier rates in other groups. More than 2,000 CFTR variants are known. The most common, F508del, is found in roughly 85% to 90% of people with CF in the US on at least one copy.
Symptoms
Lungs and sinuses
- persistent cough with thick mucus
- repeated chest infections, often with Pseudomonas and Staphylococcus aureus
- wheezing and breathlessness
- bronchiectasis: permanently widened, scarred airways
- chronic sinusitis and nasal polyps
Digestive system
- pancreatic insufficiency in most people with CF: the pancreas cannot release digestive enzymes, leading to greasy, foul-smelling, bulky stools and poor absorption of fat and fat-soluble vitamins
- poor growth and weight gain despite a good appetite
- meconium ileus: bowel blockage at birth in about 1 in 7 to 1 in 5 newborns with CF
- distal intestinal obstruction syndrome in older children and adults
- liver disease and gallstones
Other features
- very salty sweat: parents may notice salty-tasting skin when kissing their baby
- CF-related diabetes: common in adolescents and adults
- infertility in most men from absent vas deferens. Sperm production is usually normal, so assisted reproduction can help
- reduced fertility in women from thick cervical mucus
- low bone density
- finger clubbing
Diagnosis
Newborn screening
All US states screen newborns for CF with a heel-prick blood test measuring immunoreactive trypsinogen (IRT), often followed by DNA testing. A positive screen is not a diagnosis.
Sweat chloride test
The gold-standard confirmation. A small, painless stimulation makes the skin sweat, and the chloride level is measured:
| Sweat chloride | Interpretation |
|---|---|
| 60 mmol/L or higher | Consistent with CF |
| 30 to 59 mmol/L | Intermediate. Needs further testing |
| Under 30 mmol/L | CF unlikely |
Genetic testing
Identifies the two CFTR variants, which predicts eligibility for specific modulators.
Carrier testing
Recommended by ACOG to be offered to all people who are pregnant or planning pregnancy.
Treatment
People with CF are cared for by specialist CF centers with doctors, nurses, physiotherapists, dietitians, pharmacists, social workers and psychologists.
CFTR modulators
These medicines help the faulty CFTR protein fold, reach the cell surface and open. The triple combination elexacaftor/tezacaftor/ivacaftor is approved for people with at least one F508del variant or certain other responsive variants, covering roughly 90% of people with CF from age 2. Newer combinations have also been approved. Benefits include:
- improved lung function
- fewer exacerbations and hospital stays
- weight gain
- lower sweat chloride
- better quality of life
Some people have variants that do not respond, for whom research into genetic therapies continues.
Lung care
- airway clearance once or twice daily: chest physiotherapy, breathing techniques, vibrating vests and positive expiratory pressure devices
- inhaled medicines: dornase alfa to thin mucus, hypertonic saline, bronchodilators
- inhaled antibiotics such as tobramycin for chronic Pseudomonas infection
- oral or IV antibiotics for exacerbations
- exercise, which helps clear mucus and maintain fitness
- lung transplant for advanced lung disease
Digestive and nutrition care
- pancreatic enzyme capsules with every meal and snack
- high-calorie, high-fat diet and extra salt
- fat-soluble vitamin supplements (A, D, E and K)
- insulin for CF-related diabetes
Infection control
People with CF can pass harmful bacteria to each other, so CF clinics keep patients apart. The general guidance is to stay at least 6 feet (2 m) from others with CF.
Outlook
Life expectancy has risen dramatically. Cystic Fibrosis Foundation registry data show predicted median survival for people born in recent years now well into the 50s and beyond, with modern modulators expected to extend it further. Many adults with CF work, have families and live full lives.
Frequently asked questions
What are the first signs of cystic fibrosis?
In babies: bowel blockage at birth, salty-tasting skin, poor weight gain despite feeding well, greasy stools and a persistent cough or repeated chest infections. Most US cases are now detected by newborn screening before symptoms appear.
How is cystic fibrosis inherited?
A child must inherit a faulty CFTR gene from both parents. If both parents are carriers, each pregnancy has a 25% chance of CF. Carriers have one faulty gene and no symptoms. Carrier testing is available before or during pregnancy.
What is the life expectancy with cystic fibrosis?
It has increased steadily. Registry data now predict median survival in the 50s or longer for people born recently, and CFTR modulators are expected to improve it further. Outlook depends on genetics, lung health and access to care.
Can cystic fibrosis be cured?
There is no cure yet. CFTR modulators treat the underlying protein defect for most people and greatly improve health, but must be taken lifelong. Gene and mRNA therapies are being researched for those who cannot benefit from modulators.
Can people with CF have children?
Most men with CF are infertile because the vas deferens is missing, but they usually produce sperm, so assisted reproduction can help. Women with CF can often conceive, and fertility has improved with modulators. Pregnancy needs specialist planning.
Sources
This guide was written from current patient and clinical guidance, including:
- Cystic Fibrosis Foundation: About cystic fibrosis; Patient registry annual data report
- National Heart, Lung, and Blood Institute (NHLBI): Cystic fibrosis
- CDC: Newborn screening
- European Cystic Fibrosis Society: Standards of care
- NHS: Cystic fibrosis