Cystic fibrosis occurs when a child inherits a gene from both parents. This gene is called a cystic fibrosis transmembrane gene, and it codes for a protein called the cystic fibrosis transmembrane regulator (CFTR). CFTR causes problems with the way salt and water move in and out of cells that make mucus, causing the mucus to be thick and sticky. This kind of mucus makes it hard for the body to keep organs and lungs clean and healthy.

If a child inherits the CFTR gene from only one parent, the child will not have cystic fibrosis but may be a carrier. This means the child could pass the disease on to his or her children.

Many people do not know they have the CFTR gene. If you are the parent of a child who has cystic fibrosis, it is important to remember that nothing you did caused the disease.