Cystic fibrosis (CF) is a genetic disorder that causes mucus to build up and damage organs in the body, particularly the lungs and pancreas. Signs and symptoms may include salty-tasting skin; persistent coughing; frequent lung infections; wheezing or shortness of breath; poor growth; weight loss; greasy, bulky stools; difficulty with bowel movements; and in males, infertility. Over time, mucus buildup and infections can lead to permanent lung damage, including the formation of scar tissue (fibrosis) and cysts in the lungs. CF is caused by mutations in the CFTR gene and inheritance is autosomal recessive.[1][2][3] Treatment aims to relieve symptoms and usually includes respiratory therapies, inhaled medicines, pancreatic enzyme supplement, and nutritional supplements. Newer medications such as CFTR modulators have been approved for use in the United States. Ongoing research is focused on finding a cure for the disease.[2]

Last updated: 9/22/2017

Mutations in a gene called cystic fibrosis transmembrane regulator (CFTR) cause CF. More than 900 mutations in this gene have been found. This gene provides the instructions for the CFTR protein. In normal cells, the CFTR protein acts as a channel that allows cells to release chloride and other ions. But in people with CF, this protein is defective and the cells do not release the chloride. The result is an improper salt balance in the cells which leads to thick, sticky mucus.[3] When mucus clogs the lungs, it can make breathing very difficult, and causes bacteria to get stuck in the airways, resulting in inflammation and infections. Over time, mucus buildup and infections can lead to permanent lung damage, including the formation of scar tissue (fibrosis) and cysts in the lungs. Mucus can also block the digestive tract and pancreas, leading to digestive problems.[1]
Last updated: 5/23/2017
CF is inherited in an autosomal recessive manner.[4][1][5] This means that to have CF, a person must have a mutation in both copies of the CFTR gene in each cell. People with CF inherit one mutated copy of the gene from each parent, who is referred to as a carrier. Carriers of an autosomal recessive condition typically do not have any signs or symptoms.

When two carriers of an autosomal recessive condition have children, each child has a:

  • 25% (1 in 4) chance to have CF
  • 50% (1 in 2) chance to be a carrier of CF like each parent
  • 25% chance to not have CF and not be a carrier

When a carrier of CF has a child with a person with CF, each child has a:

  • 50% (1 in 2) chance to have CF
  • 50% (1 in 2) chance to be a carrier of CF
Last updated: 5/16/2017

CFTR is the only gene known to be associated with cystic fibrosis. Reasons for genetic testing or screening of this gene may include:[4]

  • Diagnosis in individuals with symptoms of CF or with congenital absence of the vas deferens (CAVD)
  • Prenatal diagnosis of a fetus at risk
  • Carrier testing for at-risk relatives and their reproductive partners or for  population screening
  • Preimplantation genetic diagnosis for pregnancies at high risk for CF
Last updated: 6/22/2012


More than 30,000 people in USA are living with cystic fibrosis (more than 70,000 worldwide).[2]

In the United States, the following are statistics about the chance to be a carrier of a CFTR gene mutation:[6][7]

  • 1 in 29 Caucasian-Americans
  • 1 in 46 Hispanic-Americans
  • 1 in 65 African-Americans
  • 1 in 90 Asian-Americans

  1. Cystic fibrosis. Genetics Home Reference. 2012;
  2. About Cystic Fibrosis. Cystic Fibrosis Foundation.
  3. Learning about Cystic Fibrosis. National Human Genome Research Institute. 2013;
  4. Moskowitz SM, Chmiel JF, Sternen DL, Cheng E, and Cutting GR. CFTR-Related Disorders. GeneReviews. February 19 2008;
  5. CF Genetics. Cystic Fibrosis Foundation. Accessed 4/12/2016.
  6. American College of Obstetricians and Gynecologists. Update on carrier screening for cystic fibrosis. Committee Opinion No. 486. ObstetGynecol. 2011; 117:1028-31.
  7. Carrier testing for CF. Cystic Fibrosis Foundation. Accessed 4/12/2016.