What is cystic fibrosis?
Cystic fibrosis (CF) is an inherited condition that mainly affects the lungs, pancreas, and sweat glands. It causes the production of thick, sticky mucus that leads to recurrent respiratory infections and blocks the release of pancreatic enzymes, inhibiting the digestion of protein and fat.
CF is one of the most common recessive genetic disorders in the U.S. A recessive disorder occurs when each of the two copies of a gene (one inherited from each parent) is abnormal. According to Cystic Fibrosis Foundation, it is estimated that 30,000 Americans are living with CF and approximately 1,000 new cases are diagnosed every year. Most people with CF are diagnosed in early childhood.
CF is caused by mutations (disease-causing variations in the DNA) in a gene called CFTR located on chromosome seven. More than 2,000 different CF mutations have been identified so far, but only a few are common. The majority of cystic fibrosis cases in the U.S. are caused by a mutation called deltaF508 (F508).
The CFTR gene is responsible for the normal production of a protein called cystic fibrosis transmembrane conductance regulator (CFTR). In CF, the CFTR protein may be dysfunctional or totally absent. With dysfunctional or absent CFTR, chloride does not move out of the ducts into surrounding fluid, resulting in the production of thick, sticky mucus. Since CFTR levels are usually highest in the epithelial cells lining the internal surfaces of the bronchi of the lungs, pancreas, sweat glands, salivary glands, intestine, and reproductive organs, these are the areas most affected by CF.
Most people with CF develop respiratory and pancreatic symptoms early in life, although the severity of signs and symptoms varies from person to person, even in those carrying the exact same mutations. The majority of adult men with CF are also infertile due to missing or underdeveloped vas deferens, the tubules that transport sperm from the testicles.
An individual with one normal CFTR gene copy and one abnormal gene copy is a CF carrier. Carriers do not generally have symptoms, but they may pass a copy of their abnormal gene on to their children. Both biological parents must either be carriers or have CF in order for their child to have CF.
The risk associated with carrying an abnormal CF gene can be generally associated with a person's ethnic background. Caucasians from Northern Europe and Ashkenazi Jews have the highest incidence of CF with about 1 in 25 individuals being CF carriers.