Cystic Fibrosis Causes

Cystic fibrosis is caused by a mutation of a specific gene. The cystic fibrosis transmembrane conductance regulator gene (CFTR gene) was discovered in 1989. Since then, over 1,300 mutations of the gene have been identified. Approximately 70% of the people with cystic fibrosis inherit the same mutation (delta F508 mutation).

Genes are the basic units of inheritance. The gene that causes cystic fibrosis is a recessive gene. To develop cystic fibrosis, a person needs to inherit two defective copies of the CFTR gene, one from each parent. People who inherit only one defective copy are "carriers" of cystic fibrosis. They don't experience any cystic fibrosis health problems themselves but may pass the defective gene to their children.

Typically, most carriers of cystic fibrosis don't know they carry the defective gene until they have a child with cystic fibrosis. If two carriers of cystic fibrosis have a child, there's a:

• 50% chance the child will be a carrier (inherit one mutated CFTR gene).
• 25% chance the child will have cystic fibrosis (inherit two mutated CFTR genes).
• 25% chance the child will not have the disease or be a carrier (inherit no mutated CFTR genes).