What Causes Cystic Fibrosis?

Cystic fibrosis (CF) is caused by 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 CF, the gene does not work effectively. This causes the thick, sticky mucus and very salty sweat that are the main features of CF.

Each of us inherits two CFTR genes, one from each parent.

• Children who inherit an abnormal CFTR gene from each parent will have CF.
• Children who inherit an abnormal CFTR gene from one parent and a normal CFTR gene from the other parent will not have CF. They will be CF carriers.

CF carriers:

• Usually have no symptoms of CF
• Live normal lives
• Can pass the abnormal CFTR gene on to their children

When two CF carriers have a baby, the baby has a:

• One in four chance of inheriting two abnormal CFTR genes and having CF.
• One in four chance of inheriting two normal CFTR genes and not having CF or being a carrier.
• Two in four chance of inheriting one normal CFTR gene and one abnormal CFTR gene. The baby will not have CF but will be a CF carrier like its parents.