Cystic fibrosis (CF) is a genetic disease caused by a mutation in a gene named the cystic fibrosis transmembrane conductance regulator (CFTR). The inheritance pattern is autosomal recessive. Thus, to have symptoms of CF, an individual must have two defective CFTR genes, by inheriting a mutant copy of the CFTR gene from both mother and father. People with a single CFTR mutation are termed “carriers”, and do not have symptoms of CF.
There are approximately 1,500 different CFTR mutations which can cause CF. The most common mutation is named ΔF508, and approximately two-thirds of all CFTR mutations worldwide are ΔF508. While having 2 copies (homozygote) of ΔF508 is associated with severe disease, many of the less common mutations are associated with less severe clinical symptoms. Detailed information about all known CFTR mutations is available by scientists at the Hospital for Sick Children in Toronto, Canada.
The CFTR gene is responsible for the production of the CFTR protein, which is a channel for the passage of salt (sodium and chloride ions) onto the surface of a variety of tissues. The CFTR protein contributes to the normal secretions produced in the airways, pancreatic ducts, sweat ducts, sinuses, and bowels. When the CFTR protein is not present, the result is mucous that is unusually thick, dehydrated, and sticky. Most of the complications of CF arise from damage caused by this abnormal mucus to the pancreas and lungs. Later in life, the most significant complications are due to infections that have taken advantage of the damaged lungs, and are often impossible to eradicate.