Cystic Fibrosis

What is cystic fibrosis?

Cystic fibrosis (CF) is a relatively common genetic disease caused by mutations in a gene located on chromosome 7. Every cell in the body (except sperm in men and egg cells, oocytes, in females) has 46 chromosomes, or 23 pairs of chromosomes, one half inherited from the mother and the other half from the father. Genes on each of these chromosomes form the body's blueprint for producing proteins that control body functions. A gene on chromosome 7 is responsible for the normal production of a protein called cystic fibrosis transmembrane regulator (CFTR). Mutations (defects at the DNA level) in this gene lead to absent or defective CFTR production, causing CF. More than 1,000 different CF mutations have been identified, although some are much more common than others.

Since CF is a recessive genetic disease, an affected individual must have a mutation in the CFTR gene on each chromosome 7 in order to be affected with CF (one abnormal copy is inherited from each parent). An individual with one normal gene and one abnormal gene is a CF carrier. Carriers do not have symptoms and are not ill, but they may pass a copy of their abnormal gene on to their children. Therefore, to have a child with CF, both biological parents must have an abnormal CF gene. In other words, they must both be carriers or have CF themselves in order for their child to have CF. Caucasians from Northern Europe and Ashkenazi Jews have the highest incidence of CF with 1 in 20-25 individuals being CF carriers.

Individuals with CF exhibit absent or defective production and function of CFTR, leading to abnormal electrolyte and water movement in and out of the epithelial cells. This, in turn, leads to thick, sticky mucus in the lungs and pancreas that promote respiratory infections and/or obstructed pancreatic and liver ducts, and impaired protein digestion. The majority of males with CF are also infertile due to missing or underdeveloped vas deferens, the tubules that transport sperm from the testes. Most people with CF develop respiratory and pancreatic symptoms early in life, although symptom severity varies from person to person, even in those with the exact same mutations.

CF is one of the most common recessive genetic disorders in the U.S. It is estimated that 30,000 Americans are living with CF and approximately 1,000 new cases are diagnosed every year. Currently, there is no prevention or cure, only treatment of symptoms. However, research is being conducted to enhance treatments and to develop a cure. Great strides in this effort have been made over the past 10 years, which are allowing some people with CF to live longer, with improved quality of life.