Cystic Fibrosis: Overview

What is cystic fibrosis?

Cystic fibrosis (CF) is a genetic disorder that affects the lungs and digestive system by making fluids and mucus in these organs thick and sticky. It is an inherited disease.

CF disrupts the normal function of epithelial cells –cells that line passageways inside the lungs, liver, pancreas, sweat glands, digestive and reproductive systems. The faulty CF gene directs the body to produce a defective form of a protein, called Cystic Fibrosis Transmembrane Conductance Regulator (CFTR). Cells with defective CFTR can't regulate the way salt passes across cell membranes. This disrupts the essential balance of salt and water needed to maintain a normal, thin coating of fluid and mucus along these linings inside the lungs, pancreas and other organs.

Normally, mucus in the lungs traps germs, which are then cleared out of the lungs through coughing. But in CF, the thick, sticky mucus and trapped germs remain in the lungs, which can cause lung infections.

In the pancreas, thick mucus blocks the passages that would normally carry enzymes to the intestines to digest foods. When this happens, the body can't process or absorb nutrients properly, especially fats. Kids with CF have problems gaining weight, even with a normal diet and a good appetite.

Now, thanks to high-tech medical advances in drug therapy and genetics, children born with CF can look forward to longer and more comfortable lives. Since the 1980s, research into all aspects of CF has helped doctors to understand the disorder better and to develop new therapies that help kids live well into adulthood. There have been very promising recent breakthroughs particularly in the area of CFTR protein rescue therapy.

What causes cystic fibrosis?

Humans have 23 pairs of chromosomes made of the inherited genetic chemical deoxyribonucleic acid (DNA). The CF gene is found on chromosome number 7. It takes two copies of a CF gene –one inherited from each parent– for a child to show symptoms of CF.

People born with only one CF gene (inherited from only one parent) are CF carriers. CF carriers do not show CF symptoms themselves, but can pass the CF gene to their children. Scientists estimate that about 12 million Americans are currently CF carriers. If two CF carriers have a child, there is a 1 in 4 chance that the child will have CF.

Who gets cystic fibrosis?

More than 1,400 different genetic mutations of the CF gene can lead to cystic fibrosis, although some mutations cause milder symptoms than others. The most common mutation in the CF gene is called F508del; around 70% of people with CF have this genetic mutation. CF gene mutations can be detected by genetic testing from blood samples.

Of all ethnic groups, Caucasians have the highest inherited risk for CF, and Asian Americans have the lowest. In the United States today, about 1 of every 3,600 Caucasian children and 1 of every 9,000 Hispanic children are born with CF. This compares with 1 of every 17,000 African Americans and only 1 of every 90,000 Asian Americans.

Although the chances of inherited risk may vary, CF has been identified in every geographic area of the world, among every ethnic population. CF affects more than 30,000 people in the United States.

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