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Cystic Fibrosis Overview
Cystic fibrosis (CF) is an inherited (genetic) condition that affects the way salt and water move in and out of cells. This, in turn, affects glands that produce mucus, tears, sweat, saliva and digestive juices. Normally, the secretions produced by these glands are thin and slippery, and help protect the body's tissues. In people with cystic fibrosis, the secretions are abnormally thick and sticky, so that they don't move as easily. Instead of acting as lubricants, these thicker secretions may clog tubes, ducts and passageways throughout the body. Cystic fibrosis also causes increased salt in sweat on the skin.
Cystic fibrosis affects both males and females; approximately 30,000 people in the United States have been diagnosed with the condition. The greatest risk factor for cystic fibrosis is a family history of the disease, especially if either parent is a known carrier. The gene that causes cystic fibrosis is recessive. This means that in order to have cystic fibrosis, children must inherit two copies of the gene, one from each parent. If a child inherits only one copy, he or she won't develop cystic fibrosis. However, that child will still be a carrier, and might pass the gene on to his or her own children.
People who carry the cystic fibrosis gene are healthy and have no symptoms of disease. In fact, it's estimated that as many as 10 million people may be carriers of a cystic fibrosis gene and not know it. If both parents carry a defective cystic fibrosis gene, each pregnancy has a 25 percent chance of producing a child with cystic fibrosis.
The cystic fibrosis gene is most common in Caucasians of northern European descent. The disease occurs most frequently in these people, but can occur in any ethnic population.
Parents can be tested to see if they are carriers; however, it's not possible to identify every person who carries a gene for cystic fibrosis. Because there are hundreds of specific cystic fibrosis gene mutations (not all of which are known), genetic testing for cystic fibrosis is not 100% sensitive. Doctors can also perform tests during pregnancy so parents can find out whether their child is likely to have cystic fibrosis. However, these tests are also not 100% sensitive. Researchers continue working to develop a test for all carriers.
Although parents often blame themselves when a child is born with cystic fibrosis, it's important to remember that nothing a parent does causes this disease.
The organs most often affected by cystic fibrosis are the lungs and the pancreas, which can lead to breathing and digestive problems. In a person with cystic fibrosis, mucus is still able to trap bacteria, but it has trouble moving out of the lungs. As a result, bacteria remain in the lungs, and can cause serious infections.
The pancreas is an organ that produces proteins called enzymes, which help the digestion process. In a person with cystic fibrosis, the thick, sticky mucus blocks ducts (or paths) between the pancreas and the intestines. It prevents enzymes that digest fats and proteins from reaching the intestines. As a result, people with cystic fibrosis have trouble digesting food and getting the vitamins and nutrients they need from it. Because the pancreas controls the level of sugar in the blood, a small percentage of people with cystic fibrosis may also develop type-one diabetes (formerly called juvenile or insulin-dependent diabetes).
In some people with cystic fibrosis, the intestines, liver, sweat glands, and reproductive organs are also harmed.
The tube connecting the testes and prostate gland can become blocked, leaving many men with cystic fibrosis infertile. However, certain fertility methods and surgical procedures can sometimes make it possible for these men to become fathers. Although women with cystic fibrosis may be less fertile than other women are, many of them are able to conceive and have successful pregnancies.
Bile ducts, which carry bile from the liver and gallbladder to the small intestine, may also become blocked and inflamed. This could cause liver problems, like cirrhosis and portal hypertension. Only a small percentage of people with cystic fibrosis develop these types of problems, however.
Signs of cystic fibrosis can vary from person to person, depending on the severity of the disease. For example, one child with cystic fibrosis may have respiratory problems but not digestive problems, while another child may have both. In addition, the signs and symptoms of cystic fibrosis may vary with age.
In some newborns, the first sign of cystic fibrosis may be that they have difficulty passing their first bowel movement (meconium). This occurs when the meconium becomes so thick that it can't move through the intestines, sometimes causing a blockage. Parents may later notice their baby is not gaining weight or growing normally. The baby's stools may be especially bulky, bad-smelling, and greasy due to poor digestion of fats. Other signs in newborns may include frequent lung (respiratory) infections, coughing and wheezing, and salty-tasting sweat. People with cystic fibrosis tend to have two to five times the normal amount of salt (sodium chloride) in their sweat. Parents sometimes notice this symptom of cystic fibrosis first, because they taste the salt when they kiss their child.
Children with cystic fibrosis may also have many of these symptoms. Growth delays often continue, and kids with cystic fibrosis tend to be significantly smaller than others their age. They may experience shortness of breath and have difficulty with exercise. Persistent coughing or wheezing is another possible symptom, especially when accompanied by frequent chest and sinus infections with recurring pneumonia or bronchitis. A child may have very thick phlegm (sputum). Infants and young children often swallow what they cough up, however, so parents may not be aware of it.
Some people with cystic fibrosis develop growths (polyps) in their nasal passages. They may experience severe or chronic sinusitis, which is inflammation of the sinuses. Their pancreas may become inflamed too; this condition is known as pancreatitis. Clubbing (enlargement or rounding) of the fingertips and toes eventually occurs in most people with cystic fibrosis, as well. However, clubbing also occurs in some people born with heart disease and other types of lung problems.
Children (usually older than age four) sometimes have intussusceptions. When this happens, one part of the intestine is displaced into another part of the intestine. The intestine telescopes into itself, similar to a TV antenna being pushed down.
Frequent coughing or hard-to-pass stools can occasionally cause rectal prolapse. This means that part of the rectum protrudes, or sticks out, through the anus. About 20% of kids with cystic fibrosis experience this. In some cases, rectal prolapse is the first noticeable sign of cystic fibrosis. It's not very common in children without cystic fibrosis, but it does occur.
When symptoms begin to show themselves, cystic fibrosis may not be a doctor's first diagnosis. As you've seen, there is a wide variety of cystic fibrosis symptoms, and not every person with cystic fibrosis exhibits all of them. Another factor is that the disease can range from mild to severe in different people. The age at which symptoms first appear varies as well. Some people with cystic fibrosis were diagnosed as babies, while others are not diagnosed until they are older. If the disease is mild at first, a person with cystic fibrosis may not experience problems until reaching his or her teen years – or even adulthood.
Babies are usually tested for cystic fibrosis if they are born with the intestinal blockage mentioned earlier, which is called meconium ileus. In some U.S. states, doctors may screen all newborns for cystic fibrosis with a blood test. However, the blood test is not as sensitive as a sweat test.
Also referred to as "sweat chloride testing", the sweat test analyzes a person's sweat for its level of salt. To perform the test, a doctor or technician stimulates sweating on a person's body – usually in a small area on the forearm. The doctor or technician does this by applying an odorless sweat-producing chemical to the area, then sending a very weak electric current through an electrode attached there. The mild current stimulates sweating and causes a warm tingling feeling, but does not hurt at all. After several minutes, sweat is collected from the stimulated area and sent to a laboratory for analysis.
The sweat test is performed twice; a consistently high level of salt indicates cystic fibrosis. This test doesn't show whether someone has a mild or severe case of the disease, however, and it can't predict how well someone with cystic fibrosis will do. The sweat test is the standard diagnostic test for cystic fibrosis, but it may not always be useful in newborns. That's because babies may not produce enough sweat for a reliable diagnosis in the first month of life. For this reason, doctors usually don't perform a sweat test until an infant is at least several months old.
In some cases, the doctor may perform a genetic analysis of a blood sample to confirm a diagnosis of cystic fibrosis. About 90 percent of people with cystic fibrosis can be detected through genetic analysis or DNA testing.
One test which is especially helpful when the sweat test and/or the genetic tests are inconclusive is called a nasal potential difference measurement. This test focuses on the movement of salt. Salt is also called "sodium chloride" because it is made up of two elements: sodium and chlorine. As tiny groups of these atoms move across the membranes of the cells lining a person's airway, they generate what is called an electric potential difference (the amount of energy required to move an electrical charge from one point to another). In the nasal passages, this electric potential difference is known as the nasal potential difference (NPD), and it can be easily measured with a surface electrode. Because Na+ and Cl- transport is abnormal in cystic fibrosis patients, NPD measurements are very different in cystic fibrosis patients than in people who do not have cystic fibrosis.
Other tests measure how well the lungs, pancreas and liver are working to help determine the extent and severity of cystic fibrosis once it is diagnosed. These tests include chest X-rays, pulmonary (lung) function tests (PFTs), and tests of pancreatic function.
Because cystic fibrosis is an inherited disease, the doctor may suggest testing the siblings of a person with cystic fibrosis, even if they show no symptoms. Other family members, especially first cousins, also may want to be tested. In most cases family members can be screened with a sweat test, although in some cases genetic testing may be appropriate.
Right now, there is no treatment that can cure cystic fibrosis. However, many treatments exist for the symptoms and complications of this disease. The main goals of treatment for someone with cystic fibrosis are to prevent and treat infections, keep the airways and lungs as clear as possible, and maintain adequate calories and nutrition.
To accomplish these objectives, treatments for cystic fibrosis may include:
- Childhood immunizations. Cystic fibrosis doesn't affect the immune system itself, but children with cystic fibrosis are more likely to develop complications when they become sick. Doctors are especially concerned with making sure cystic fibrosis children receive their pneumococcal and influenza vaccines.
- Antibiotics. Newer antibiotics may more effectively fight the bacteria that cause lung infections in people with cystic fibrosis. Oral and intravenous antibiotics have made antibiotic therapy available on an outpatient basis. Aerosolized antibiotics that can be inhaled, such as tobramycin (Tobi), allow medication to reach directly into a person's airways. The drawbacks to long-term antibiotic therapy include the development of bacteria that are resistant to antibiotics.
- Other medications. The main purpose of these is to keep the airways clear. Some medications that might be prescribed include:
- Steroid inhalers
- Nonsteroidal anti-inflammatory drugs
- Mucus-thinning drugs that make mucus easier to cough up
- Bronchodilators such as albuterol (Proventil, Ventolin)
- Bronchial airway drainage. Other ways to loosen mucus include regular exercise and drinking lots of fluids. Chest physical therapy is also an important part of the treatment routine. People with cystic fibrosis need a way to physically remove thick mucus from their lungs. After lying down in a position that helps drain mucus from the lungs, the person may have a helper, such as a parent or caregiver, gently bang or clap on his chest or back to loosen the mucus. Other people use an electric chest clapper, also known as a mechanical percussor. Some people may use an inflatable vest with a machine attached that vibrates at high frequency to help cough up secretions. Both adults and children with cystic fibrosis need to have bronchial airway drainage at least twice a day for 20 to 30 minutes. Older children and adults can learn to do this themselves, especially if they use mechanical aids such as vests and percussors.
- Enzymes. For digestive problems, people with cystic fibrosis can take enzymes by mouth with meals in order to help digest his food and get the nutrients they need. The doctor may also prescribe vitamin supplements and a high-calorie diet.
- Insulin shots. These are only needed if pancreas stops producing insulin of its own.
- Oxygen therapy. This treatment may be required as the disease progresses.
- Lung and/or liver transplants. In some cases, lung transplants have extended the lives of people with cystic fibrosis. Although it is rarer for a person with cystic fibrosis to need a liver transplant, the procedure can also be beneficial.
Even though there is no cure for cystic fibrosis, there is hope. In the past couple decades, treatment has come an astonishingly long way. One of the biggest breakthroughs in cystic fibrosis research came in 1989, when researchers identified the gene that, when defective, causes the disease. Researchers are now exploring gene therapy to slow the progression of cystic fibrosis, or even cure it.
Fifteen years ago, most children with cystic fibrosis would die before reaching their teens. Now, with new treatments available, more than half live into their 30s, and have fuller and more comfortable lives.
Today, most children with cystic fibrosis go to school, participate in sports and have active social lives. In time they may graduate from college and embark on careers, and many marry and raise families of their own.
Learn about other Liver Disease States.
November 21, 2010
November 21, 2010