Cystic Fibrosis

(CF)

In this condition factsheet:

• The Facts
• Causes
• Symptoms and Complications
• Making the Diagnosis
• Treatment and Prevention

The Facts

Cystic fibrosis (CF) is an inherited (genetic) disease in which excess mucus clogs the lungs, prevents food from being digested, and damages the reproductive system. It is the most common life-threatening genetically inherited disease affecting children and young adults. The incidence of CF occurs in about 1 in 3,800 live births in Canada.

In CF, an abnormal protein called CFTR is produced. This protein changes the way chloride (a component of salt, which is also called sodium chloride) moves in and out of cells. This affects the balance between salt and water in the body, making the mucus that lines the lungs, pancreas, and other organs thicker and stickier.

CF affects all the body's exocrine glands. These glands create and secrete chemicals necessary for proper functioning of the body. The pancreas, for example, is an exocrine gland that provides digestive enzymes for the stomach. The sweat glands provide liquid to cool the skin. In CF, some glands produce abnormal substances. The sweat glands, for example, release high levels of salt. Other glands, like the pancreas, become plugged with mucus. Because of the many organs affected and thanks to newborn genetic screening, CF is usually diagnosed early in childhood, with over half of children being diagnosed before the age of 1. Thanks to good research, more and better medications, and early diagnosis, people with CF are living longer, fuller lives.

Causes

CF cannot be "caught" like a cold or the flu. It's genetic and is caused by inheriting two copies of the same abnormal gene, one from each parent. People who get one defective and one normal copy of the gene are said to be "carriers" of the CF gene. Carriers don't get CF, but they have the abnormal CF gene that can be passed on to their children.

If both parents are carriers, their children have a 1 in 4 chance of getting the disease, a 1 in 2 chance of being carriers, and a 1 in 4 chance of being normal. Boys and girls are equally likely to have CF.

The table below shows your risk of being a CF carrier based on your ethnicity. Your family history also significantly affects your risk of being a CF carrier. People whose relatives have CF are at high risk of carrying the CF mutation.

Ethnicity	Carrier risk
White, European ancestry	1 in 29
Ashkenazi Jewish	1 in 29
Hispanic	1 in 46
Black	1 in 62
Asian	1 in 90

Researchers have also noticed abnormal levels of some essential fatty acids in people with CF. The role of these fatty acids is still unknown.

Symptoms and Complications

CF causes the body to produce large amounts of thick mucus. This affects the lungs as well as the digestive and reproductive systems. Symptoms of CF may appear at birth or years later, and range from mild to severe depending on the person.

A child's skin will taste salty – something a parent may notice – because CF causes the sweat to contain an unusually high amount of salt.

In the lungs, the mucus plugs the child's airways. This leads to wheezing, coughing, and trouble breathing. It also puts the child at risk of lung and sinus infections. Bacteria, found in the airways of people with CF, can contribute to further damage of the lungs.

Enzymes produced by the pancreas are necessary to digest food in the stomach. In people with CF, large amounts of mucus block the pancreas and prevent enzymes from being released. This causes digestive problems. Even if they eat a normal diet, children with CF may be smaller than others of the same age. Since food is not digested correctly, it leaves the body as waste in the stools. The stools are often large and have a foul smell.

Children with CF may reach puberty at a later age than normal. Both men and women may have fertility problems. More than 95% of men with CF are infertile, which is usually caused by not having the vas deferens (tubes that move sperm out from the testicles). In women, mucus can clog the fallopian tubes or the menstrual cycles may be irregular. Nevertheless, many women with CF are able to get pregnant and give birth to normal children if their partners don't have or carry CF. Their children, however, will carry the CF gene.

As a child grows older, CF may cause other symptoms. Some develop diabetes and need insulin treatment, and others suffer liver damage. Many children with CF live well into adulthood. It is estimated that people with CF in Canada will live to an average age of 57. With improving treatments and health care, this age will continue to increase gradually. For the minority who have a healthy pancreas, the prognosis is far better.

Good lung function is also a promising sign. Men tend to survive slightly longer than women.

Making the Diagnosis

If your child has any of the symptoms listed above, see your doctor for a diagnosis. Your doctor will ask about symptoms and family history, and screen for CF. He or she will probably do a "sweat test," which measures the amount of salt in your child's sweat.

The doctor may also test your child's lungs using chest X-rays and lung-function tests. If CF runs in your family, you may want to look into having genetic tests done for you and your partner if you are planning a pregnancy or are pregnant. You may also consider having your baby screened for CF before or at birth.

Treatment and Prevention

There's no cure for CF. Treatment includes digestive enzyme supplements, dietary changes, immunizations, physical therapy, and medications. More recently, some CF patients with terminal lung disease have received lung transplants.

Children need to eat a well-balanced diet rich in calories and protein. They may need 30% to 50% more calories and protein than a child without CF. A dietitian can help with meal planning. When children are involved in activities that may make them hot or sweaty, they need to replace the salt they lose in their sweat. Children can be given salt tablets or salt-water solutions. Children with CF usually take additional vitamins.

Keeping a child's immunizations (vaccine shots) up to date is extremely important to protect them from infections. Talk to your doctor to be sure that your child gets all the necessary vaccines, especially for whooping cough (pertussis), influenza, COVID-19, chickenpox, pneumococcal disease, and measles. Your child should get a flu shot every year or as recommended by your doctor. Keep a record of all your child's immunizations.

To loosen and bring up the extra mucus that builds up in the chest, a number of physical measures are used. These include "assisted coughing," drainage, a positive expiratory pressure (PEP) device, and percussion (pounding on the chest or back to loosen mucus). Older children can learn how to perform these techniques on themselves.

A number of medications can help people with CF. Your doctor may prescribe:

• CFTR protein modulators, a class of medications that can help to normalize your water-chloride balance
• enzyme pills to be taken before eating to help digest food
• anti-inflammatories to slow the deterioration of the lungs
• antibiotics to treat or prevent lung infections
• inhaled medications to make breathing easier
• multivitamins (especially vitamins A, D, E, and K) to ensure proper nutrition for normal growth and development

The development that holds the greatest promise is gene therapy. CF is one of the few inherited diseases where just one gene is at fault. In other words, there's real reason to hope for a cure.
CF can't be prevented in a child with two copies of the defective CF gene. But it's possible to find out if you're at risk for having a child with CF. You and your partner can have genetic testing done to determine if you are both carriers.

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