Cystic fibrosis (CF) is an inherited disorder, usually diagnosed in young children but sometimes not until adolescence or adulthood. People with cystic fibrosis secrete very thick mucus from the windpipe, or tracheobronchial glands. They also have abnormal secretions of sweat and saliva.
What is going on in the body?
Since the abnormally thick mucus prevents proper clearing of sputum and bacteria from the lungs, the person's lungs may become chronically infected. The mucus blocks the secretion of enzymes used for digesting foods from the pancreas.
What are the causes and risks of the disease?
CF is the most common serious genetic disease among Caucasian children, occurring in about 1 of every 2,500 live births. The disease almost always occurs in Caucasians, and is equally common in males and females. It is usually diagnosed in infancy or childhood, but occasionally a case with mild manifestations can elude detection until adulthood.
CF is an autosomal recessive trait. This means that both parents must pass on an abnormal gene for the child to be affected. One in 25 adults carries one copy of the cystic fibrosis gene.
If both parents carry the gene, each child has a 25% risk of cystic fibrosis. If one parent has the gene but no history of cystic fibrosis and the other parent has the disease, there is a 50% chance that the child will be affected.
What can be done to prevent the disease?
The gene for cystic fibrosis has been found on chromosome 7. There are many different abnormalities in this gene that can result in cystic fibrosis. Genetic testing can now identify more than 80% of people with a CF gene.
People who come from families where someone has cystic fibrosis may choose to be tested for an abnormal gene. Couples can receive genetic counseling to decide how best to proceed with any family planning decisions. Testing for the abnormal gene can also be done on an unborn child.
How is the disease diagnosed?
Family history, persistent respiratory disease, or clinical evidence of pancreatic insufficiency may suggest the diagnosis of cystic fibrosis.
The diagnosis requires an abnormal sweat chloride test. In this test, a chemical is used to stimulate sweat production. The amount of chloride in the sweat will be abnormally high in a person with CF. Genetic screening is done if the sweat test is inadequate.
Screening for pancreatic insufficiency is done by measuring the levels of two enzymes in the stool (trypsin and chymotrypsin) or for fecal fat secretion. These tests are not as reliable as measuring the sweat chloride level.
Lung function testing can identify certain abnormalities in the way the lungs and airways work. These abnormalities may be caused by problems other than cystic fibrosis.
Long Term Effects
What are the long-term effects of the disease?
People with cystic fibrosis have an increased risk of lung infections. Many of them will have repeated bouts of pneumonia, usually leading to worsening lung disease. Respiratory failure or arrest can be the end result. Men and women with cystic fibrosis are often unable to have children because of abnormalities in their reproductive systems.
What are the risks to others?
Cystic fibrosis is not contagious, but the abnormal gene is passed from parent to child.
What are the treatments for the disease?
Treatment for cystic fibrosis focuses on treating symptoms and deficiencies. Pancreatic enzymes and diet changes may lead to better digestion. Lung and airway infections can be treated with potent antibiotics. Inhaled bronchodilator medications such as albuterol have improved breathing in some people with cystic fibrosis.
Chest physiotherapy, vibrating vests, and postural drainage techniques are used to help clear the excess mucus out of the lungs. Inhaled drugs that help break up the mucus, such as dornase alfa (i.e., Pulmozyme), may help clear the lungs.
Anti-inflammatory medication such as ibuprofen (i.e., Advil, Motrin) may reduce the inflammation in the lungs.
Inhaled antibiotics are used to prevent lung infections that may lead to hospitalization and the need for complex treatment protocols involving multiple intravenous antibiotics.
As the disease progresses, the lung function can decline to a point where no treatment can restore normal function. In some of these cases of end-stage cystic fibrosis, lung transplantation has been successful. This requires life-long immunotherapy to avoid rejection of the transplanted tissue.
Now that the gene for cystic fibrosis is known, the possibility of gene therapy may someday become a reality. Already scientists have transferred normal genes from chromosome 7 into laboratory animals and seen promising results.
What are the side effects of the treatments?
Side effects depend on which medications are used. Bronchodilators can cause a rapid heart rate and trembling of the hands. Antibiotics can cause rashes and other allergic reactions.
What happens after treatment for the disease?
Rehabilitation therapy helps most people to use their energy more efficiently, in a way that requires less oxygen. Many people, especially those with an advanced stage of CF, can benefit from breathing supplemental oxygen. It improves shortness of breath and may extend survival in some cases.
How is the disease monitored?
Regular lung function testing may be done to check on how well the lungs and airways are working. Sputum may be collected and sent to the lab to test for infection. Cystic fibrosis is a life-long disease. It helps to pay ongoing attention to physical conditioning, nutrition, and good mental health. Monitoring growth is important in order to assess the adequacy of nutritional intake.
Scientific American Medicine, Principles of Medical Genetics.