Causes of Cystic Fibrosis

The primary cause of cystic fibrosis is a defect in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. The condition occurs when a child receives an abnormal CFTR gene from each parent. A child who inherits one abnormal gene and one normal gene will not develop cystic fibrosis.

Understanding What Causes Cystic Fibrosis

The cause of cystic fibrosis (CF) is a defect in a gene called the cystic fibrosis transmembrane conductance regulator (CFTR) gene. This gene makes a protein that controls the movement of salt and water in and out of the cells in your body. In people with cystic fibrosis, the gene does not work effectively. This causes the thick, sticky mucus and very salty sweat that are the main features of cystic fibrosis.
 

More About the CFTR Gene

Each of us inherits two CFTR genes, one from each parent. Children who inherit an abnormal CFTR gene from each parent will have cystic fibrosis. Children who inherit an abnormal CFTR gene from one parent and a normal CFTR gene from the other parent will not have cystic fibrosis. However, they will be cystic fibrosis carriers.
 
Cystic fibrosis carriers:
 
  • Usually have no symptoms of cystic fibrosis
  • Live normal lives
  • Can pass the abnormal CFTR gene on to their children.
     

What's the Inheritance Risk for Carriers?

When two cystic fibrosis carriers have a baby, the baby has a:
 
  • One in four chance of inheriting two abnormal CFTR genes and having cystic fibrosis.
     
  • One in four chance of inheriting two normal CFTR genes and not having cystic fibrosis or being a carrier.
     
  • Two in four chance of inheriting one normal CFTR gene and one abnormal CFTR gene. The baby will not have cystic fibrosis, but will be a cystic fibrosis carrier like its parents.
 
A Dose of Reassurance for Parents of Picky Eaters

Cystic Fibrosis Information

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