Cystic fibrosis (CF) is a chronic, progressive, and frequently fatal genetic (inherited) disease of the body's mucous glands. CF primarily affects the respiratory and digestive systems in children and young adults. The sweat glands and the reproductive system are also usually involved. In general, individuals with CF have a lifespan of approximately 30 years.
CF does not follow the same pattern in all patients but affects different people in different ways and to varying degrees. However, the basic problem is the same – an abnormality in the glands, which produce or secrete sweat and mucous. Sweat cools the body; mucous lubricates the respiratory, digestive, and reproductive systems, and prevents tissues from drying out, protecting them from infection.
According to the data collected by the Cystic Fibrosis Foundation, there are about 30,000 Americans, 3,000 Canadians, and 20,000 Europeans with CF. The disease occurs mostly in whites whose ancestors came from northern Europe, although it affects all races and ethnic groups. Accordingly, it is less common in African Americans, Native Americans, and Asian Americans. Approximately 2,500 babies are born with CF each year in the United States. In addition, about 1 in every 20 Americans is an unaffected carrier of an abnormal "CF gene." These 12 million people are usually unaware that they are carriers.
CF symptoms vary from child to child. A baby born with the CF genes usually has symptoms during its first year. Sometimes, however, signs of the disease may not show up until adolescence or even later. Infants or young children should be tested for CF if they have persistent diarrhea, bulky foul-smelling and greasy stools, frequent wheezing or pneumonia, a chronic cough with thick mucous, salty-tasting skin, or poor growth. CF should be suspected in babies born with an intestinal blockage called meconium ileus.
The most common test for CF is called the sweat test. It measures the amount of salt (sodium chloride) in the sweat. In this test, an area of the skin (usually the forearm) is made to sweat by using a chemical called pilocarpine and applying a mild electric current. To collect the sweat, the area is covered with a gauze pad or filter paper and wrapped in plastic. After 30 to 40 minutes, the plastic is removed, and the sweat collected in the pad or paper is analyzed. Higher than normal amounts of sodium and chloride suggest that the person has cystic fibrosis.
The sweat test may not work well in newborns because they do not produce enough sweat. In that case, another type of test, such as the immunoreactive trypsinogen test (IRT), may be used. In the IRT test, blood drawn 2 to 3 days after birth is analyzed for a specific protein called trypsinogen. Positive IRT tests must be confirmed by sweat and other tests.
Also, a small percentage of people with CF have normal sweat chloride levels. They can only be diagnosed by chemical tests for the presence of the mutated gene. Some of the other tests that can assist in the diagnosis of CF are chest X-rays, lung function tests, and sputum (phlegm) cultures. Stool examinations can help identify the digestive abnormalities that are typical of CF.
Since CF is a genetic disease, the only way to prevent or cure it would be with gene therapy at an early age. Ideally, gene therapy could repair or replace the defective gene. Another option for treatment would be to give a person with CF the active form of the protein product that is scarce or missing.
At the time of writing, neither gene therapy nor any other kind of treatment exists for the basic causes of CF, although several drug-based approaches are being investigated. In the meantime, the best that doctors can do is to ease the symptoms of CF or slow the progress of the disease so the patient's quality of life is improved. This is achieved by antibiotic therapy combined with treatments to clear the thick mucous from the lungs. The therapy is tailored to the needs of each patient. For patients whose disease is very advanced, lung transplantation may be an option.
CF was once always fatal in childhood. Better treatment methods developed over the past 20 years have increased the average lifespan of CF patients to nearly 30 years.
People with CF lose excessive amounts of salt when they sweat. This can upset the balance of minerals in the blood, which may cause abnormal heart rhythms. Going into shock is also a risk.
Mucous in CF patients is very thick and accumulates in the intestines and lungs. The result is malnutrition, poor growth, frequent respiratory infections, breathing difficulties, and eventually permanent lung damage. Lung disease is the usual cause of death in most patients.
CF can cause various other medical problems. These include sinusitis (inflammation of the nasal sinuses, which are cavities in the skull behind, above, and on both sides of the nose), nasal polyps (fleshy growths inside the nose), clubbing (rounding and enlargement of fingers and toes), pneumothorax (rupture of lung tissue and trapping of air between the lung and the chest wall), hemoptysis (coughing of blood), cor pulmonale (enlargement of the right side of the heart), abdominal pain and discomfort, gassiness (too much gas in the intestine), and rectal prolapse (protrusion of the rectum through the anus). Liver disease, diabetes, inflammation of the pancreas, and gallstones also occur in some people with CF.
Most people with cystic fibrosis have difficulty absorbing dietary fat, which in turn leads to steatorrhea. Cystic fibrosis interferes with the ability of the pancreas to secrete digestive enzymes: fat is normally broken down by lipase, a digestive enzyme that is produced and secreted by the pancreas.
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