Cystic fibrosis (CF) is an inherited disease that most commonly affects breathing and digestion. Advances in medical treatment continue to improve the outlook for affected children and adults. However, there is no cure. Most affected individuals survive to about age 30, though some die in childhood and others live to age 40 or beyond.

What Is Cystic Fibrosis?
CF is an inherited disease caused by an abnormal protein that does not allow the normal passage of chloride (which, along with sodium, makes up salt) into and out of certain cells, including those that line the lungs and pancreas. As a result, these cells produce thick, sticky mucus and other secretions. The mucus clogs the lungs, causing breathing problems. Affected individuals also have frequent lung infections, which eventually damage the lungs and contribute to early death. The thickened digestive fluids made by the pancreas are prevented from reaching the small intestine, where they are needed to digest food.

Is CF Common?
About 30,000 children and adults in this country have CF, according to the Cystic Fibrosis Foundation. While all racial groups are affected, the disease is most common in caucasians.

What Are the Symptoms of CF?
The symptoms of CF vary, and some children and adults are less severely affected than others. Individuals with CF tend to cough and wheeze frequently. They may develop repeated lung infections, such as pneumonia. Many of these infections are caused by a bacterium called Pseudomonas aeruginosa, which rarely causes problems in healthy people.

Many, but not all, children and adults with CF have digestive problems due to blockage of digestive chemicals from the pancreas. Affected children often have a big appetite, but gain weight or grow slowly.

Some children with CF are well enough to attend school, participate in some exercise and recreational activities (though stamina is generally reduced), and go on to college and rewarding careers. Others, however, are too ill to attend school regularly.

How Is CF Diagnosed?
CF is diagnosed with a simple, painless test that measures the amount of salt in the sweat. Infants, children and adults with CF have more salt in their sweat than unaffected individuals. In many cases, CF is diagnosed when a child is between 2 and 4 years of age, following repeated lung infections and/or growth problems.

A few states have begun screening newborns for CF, along with other disorders of body chemistry routinely tested for soon after birth. Some studies suggest that early diagnosis and treatment improve the growth of babies and children with CF.

Who Is Most Likely to Be a Carrier?
According to the Cystic Fibrosis Foundation, one in 31 Americans — more than 10 million people — carry a gene for CF. Someone with a family history of CF is more likely to carry a CF gene than someone from an unaffected family. The risk also is increased in individuals of caucasian backgrounds. These individuals have a 1 in 29 chance of carrying the gene, compared to 1 in 46 for those of Hispanic background, 1 in 65 for African Americans, and 1 in 90 for Asian Americans.

What Happens if the Test Shows a Woman Is a Carrier?
The next step is to test her partner. A baby is not at risk of CF unless both parents carry the abnormal gene. Fortunately, this situation is fairly uncommon. In those of caucasian background, the chances that both partners carry the CF gene is only about 1 in 800; the risk is less in other groups.

It’s important to keep in mind, however, that the test is not 100 percent accurate. Scientists have discovered more than 900 different mutations (abnormalities) in the CF gene, and the test looks only for some of the most common of these. So even when the test shows that a person is not a carrier, a very small chance remains that he or she carries an abnormal gene.

What Happens if Both Parents Are Carriers?
A couple in which both partners are carriers should consider consulting a genetic counselor, who can discuss the risks to their future children. A genetic counselor also can discuss the option of prenatal testing (using amniocentesis or CVS) to diagnose or rule out CF in the fetus. As discussed above, each child of parents who both carry an abnormal CF gene has a 25 percent chance of inheriting CF. This means that in three out of four cases, the prenatal test will reveal that the fetus will not have CF. When the fetus is affected, parents can take the time before delivery to learn more about the disease and locate appropriate specialists. Prenatal testing cannot, however, tell how seriously affected the baby may be.

Information provided by the March of Dimes