Definition Cystic fibrosis is an inherited disorder, mostly of young children. Sometimes the disease is not diagnosed until adolescence or adulthood. People with cystic fibrosis secrete very thick mucous from the windpipe, or tracheobronchial glands. They also have abnormal secretions of sweat and saliva. The pancreas may release enzymes improperly, a condition called pancreatic insufficiency. The lungs have changes similar to those in bronchiectasis.
Different people have different levels of abnormalities in cystic fibrosis. Some people are very ill when they are quite young. Others can live many years with mild abnormalities. Half of males with cystic fibrosis now live to be over 30 years old. Half of females with cystic fibrosis survive beyond 28 years.
What is going on in the body? Since the abnormally thick mucous prevents proper clearing of sputum and bacteria from the lungs, the person's lungs become chronically infected. The mucous blocks the secretion of enzymes used for digesting foods from the pancreas.
What are the signs and symptoms of the disease? In cystic fibrosis, the pancreatic enzymes that help digest dietary fat are not secreted into the intestines. Food, especially fat, is poorly digested, and stools may be bulky or fatty. Nutritional considerations are important with cystic fibrosis. About 10 to 20% of babies with cystic fibrosis have intestinal obstruction. This condition is called meconium ileus, and the infant is unable to pass any stool. Surgery is usually required to correct meconium ileus.
Cystic fibrosis causes obstruction of the breathing passages. People with the disease may:
have difficulty breathing when they exert themselves
cough up blood
have a collapsed lung known as atelectasis. The thick mucous lining the airways often gets infected. This may result in widespread damage, called bronchiectasis.
Many men with cystic fibrosis have low, or zero, sperm counts and have difficulty fathering children. This is caused by problems with the tubules leading from the testicles to the penis.
What are the causes and risks of the disease? Cystic fibrosis is the most common serious genetic disease among Caucasian children. It occurs 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 chiefly a disease of infants and children, but more adult cases are being diagnosed.
Cystic fibrosis 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 gene with no history of cystic fibrosis and the other parent has the disease, there is a 50% chance of the child being 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 an abnormal gene. People who come from families where someone has cystic fibrosis may choose to be tested for an abnormal gene. Testing for the abnormal gene can also be done on foetuses. In either case, couples can receive genetic counselling to decide how best to proceed with any family planning decisions.
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 is then measured. In Queensland, screening is undertaken with the neonatal heel-prick.
Screening for pancreatic insufficiency is done by measuring the levels of two enzymes in the stool. This test is 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.
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. These usually lead to worsening lung disease. This, in turn, can result in respiratory failure and arrest.
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 is passed genetically to children.
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 used in asthma, such as salbutamol, have improved breathing in some people with cystic fibrosis.
Chest physiotherapy and postural drainage techniques are used to help clear the excess mucous out of the lungs. Drugs that help break up the mucous, such as dornase alfa, may help clear the lungs. Anti-inflammatory medication like ibuprofen may reduce the inflammation in the lungs. Inhaled antibiotics are used to prevent lung infections that may lead to hospitalisation.
Now that the gene for cystic fibrosis is known, the possibility of gene therapy looks hopeful. 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 also use oxygen therapy. This improves shortness of breath and overall survival, especially in those with advanced disease.
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 laboratory 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 an important consideration for assessing adequate nutrition.
Author: Reviewer: HealthAnswers Australia Medical Review Panel Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia Last Updated: 1/10/2001 Contributors Potential conflict of interest information for reviewers available on request
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