Cystic Fibrosis

Cystic fibrosis (CF) is an inherited disease that affects breathing and digestion. Advances in medical treatment have improved the outlook for affected children and adults. However, there is no cure. Most affected individuals survive into their 30s, though some die in childhood and others live to age 40 or beyond.
The abnormal gene that causes CF was discovered in 1989.  This discovery led to the development of a test, called a carrier screening test, that can help determine whether a couple is at increased risk of having a baby with CF. The test is routinely offered to couples who have a family history of CF. Many health care providers also make this test available to couples who are planning pregnancy or are pregnant. Couples must decide if testing is right for them.

What is cystic fibrosis?
CF is an inherited disease that affects the normal movement of salt (sodium chloride) into and out of certain cells, including those that line the lungs and pancreas. This results in thick, sticky mucus and other secretions.
The mucus clogs the lungs, causing breathing problems. It also provides a breeding ground for bacteria to grow. This leads to frequent lung infections, which eventually damage the lungs and contribute to early death.
Thick digestive fluids also may clog ducts leading from the pancreas to the small intestine. This prevents the fluids from reaching the small intestine, where they are needed to digest food. This can cause digestive problems and slow growth.

How common is CF?
About 30,000 children and adults in the United States have CF (1). The disease is most common in Caucasians, though all racial groups are affected.

What are the symptoms of CF?
The symptoms of CF vary and can range from mild to severe. Some common symptoms include:

■Coughing or wheezing
■Repeated lung infections, such as pneumonia and bronchitis
■Shortness of breath
■Poor growth, in spite of a big appetite
■Intestinal blockage, called meconium ileus, in a newborn (caused by thickening of the greenish stool newborns usually pass in the first days of life)
■Greasy, bulky stools
■Infertility in affected males due to blockage or absence of the tube (vas deferens) that carries sperm out of the testicles

Many lung infections in individuals with CF are caused by a bacterium called Pseudomonas aeruginosa. This bacterium rarely causes problems in people who do not have cystic fibrosis. Antibiotics often cannot completely clear this bacterium from the lungs. These infections contribute to lung damage.
Most children with CF are well enough to exercise and attend school. Doctors recommend exercise in individuals with CF because it helps loosen mucus in the lungs and strengthens the heart and lungs.    

How is CF diagnosed?
CF is diagnosed with a sweat test or with gene tests using a blood sample or saliva. Many children with CF are now diagnosed in the first six months of life. About 10 states routinely screen all newborns for CF, along with other disorders of body chemistry.
About 15 to 20 percent of newborns with CF have meconium ileus. When a baby has this symptom, the health care provider will recommend a gene test to diagnose or rule out CF. Some studies suggest that early diagnosis and treatment improve the growth of babies and children with CF.
Other children are not diagnosed until they begin to develop other symptoms, such as repeated lung infections or poor growth. Children with possible symptoms of CF usually are given a sweat test. This simple, painless test measures the amount of salt in the sweat. Individuals with CF have more salt in their sweat than unaffected individuals. In most cases, CF is diagnosed by 3 years of age. Some health care providers also recommend a gene test to confirm the diagnosis.
Both the gene test and the sweat test are accurate in diagnosing CF. However, neither can accurately predict how severe the child’s symptoms will be.

How are lung problems prevented and treated in individuals with CF?
Children and adults with CF need close medical supervision throughout their lives.   
Many children with CF need daily respiratory therapy. This is done at home for about 30 minutes once or twice a day. There are a number of techniques that are used to help a child loosen and clear the mucus from the lungs. For example, a parent or other caretaker can clap the child on the back and chest, or they can use an electric chest clapper or an inflatable vest that vibrates. The child’s health care team will recommend the most effective approach.
A number of medications can help affected individuals breathe better and prevent infections. Many come in a mist form that the child inhales into the lungs. The health care provider will recommend different medications depending on the person’s symptoms and how severe they are. Types of medications include:
Mucus-thinners. Drugs such as Pulmozyme (Dnase) help thin the mucus so that the child can cough up it up more easily.
Bronchodilators. These medications help clear mucus and keep airways open. Examples are Albuterol, Proventil and Ventolin.
Antibiotics. These medications prevent and treat infections. An inhaled antibiotic called TOBI (tobramycin) is commonly used.
Anti-inflammatories. Medications, such as inhaled steroids and ibuprofen, help prevent lung inflammation (redness and swelling) that can make breathing difficult.
In spite of these treatments, infections occur. Infections may be treated at home or in the hospital with a number of antibiotics, which can be given by mouth, through a vein (intravenously) or by inhalation.

Unfortunately, as the individual gets older, infections tend to get worse and more difficult to treat, often leading to serious lung damage. Infection, and the resultant lung damage, are the leading causes of death in individuals with CF. Lung transplantation is an option for some individuals who develop life-threatening lung complications. This is a major operation, but it is becoming increasingly successful in improving symptoms in some severely affected individuals.

How are growth and digestive problems prevented and treated?
Some infants and children with CF gain weight and grow normally, but many grow more slowly than unaffected children. This is because sticky mucus blocks pancreatic enzymes from reaching the small intestine, where most digestion and absorption of nutrients takes place. As a result, affected children may absorb fewer calories and nutrients, leading to slow growth.
Many individuals with CF experience symptoms related to poor digestion. These include:

■Slow weight gain, in spite of a good appetite
■Frequent, loose or large bowel movements
■Bowel movements that contain mucus or oil
■Gas, stomach pain and bloating

Most individuals with CF need to take medications containing pancreatic enzymes with each meal. These enzymes help the body absorb nutrients from food, improving weight gain and digestive symptoms. To improve growth, children with CF also must eat a healthy, high-calorie diet supplemented with certain vitamins (especially vitamins A, D, E and K). A dietitian who is experienced with CF can help a family plan a child’s diet to achieve a healthy weight gain.

Can a person catch CF from someone who has it?
No. The disease is inherited and is not contagious.

How is CF inherited?
Genes come in pairs. To inherit CF, a child must receive two CF genes, one from each parent who “carries” a CF gene. A carrier is a healthy individual who has one normal gene and one abnormal gene in the pair.
When both parents carry an abnormal CF gene, there is a 25 percent (1-in-4) chance that the child will have CF. There is a 50-50 (50 percent) chance that the child will be a carrier like the parents. There also is a 25 percent chance that the child will be free of the abnormal gene and neither be a carrier, nor have the disease.
The couple has the same risks with each pregnancy. If only one parent is a carrier, there is no chance that their children will have CF. However, there is a 50-50 chance of each child being a carrier.

Who should have the carrier screening test?
The American College of Obstetricians and Gynecologists (ACOG) recommends that the carrier screening test be available to all couples who are planning pregnancy or are pregnant. Many health care providers hand out printed material on the test for couples to read. Those who are interested in testing can then discuss it further with their provider.
Health care providers are more likely to offer the test to couples considered at increased risk of having an affected child. Such couples include those with a family history of CF and Caucasians.
Whether or not a couple chooses to take the carrier screening test is a personal decision. A couple must decide what is right for them after learning about CF and discussing the test with their health care provider.

How is the test done?
The health care provider will take a sample of blood or saliva. The sample will be sent to a lab to test for the abnormal gene.

Who is most likely to be a carrier?
One in 30 Americans—more than 10 million people—carries 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. Caucasians 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 that 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 1,300 different mutations (changes) 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, there’s a very small chance 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. A genetic counselor can discuss the risks to their future children and the option of prenatal testing (using amniocentesis or CVS) to diagnose or rule out CF in a fetus. 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 show that the fetus does 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.

Can women with CF become pregnant?
Some women with CF may have trouble becoming pregnant. However, many women with CF can become pregnant and have healthy pregnancies. In some cases, pregnancy may temporarily make breathing more difficult. But studies suggest that pregnancy does not worsen lung damage or shorten survival. Women with CF who are considering pregnancy should consult their CF specialists before they become pregnant. They will need continuing care from these specialists, as well as from an obstetrician experienced with CF, throughout pregnancy.
Babies of women with CF are not at risk of inheriting the disease unless the father carries the abnormal gene. When the woman is affected with CF, the couple should consult a genetic counselor and consider carrier screening for the partner before pregnancy.