cf_new3.qxd 2/21/96 3:14 PM Page 1 FACTS ABOUT Cystic Fibrosis What Is Cystic Fibrosis What Are the Signs and Symptoms Cystic fibrosis (CF) is a chronic, progressive, of CF? and frequently fatal genetic (inherited) dis­ CF does not follow the same pattern in all ease of the body’s mucus glands. CF pri­ patients but affects different people in dif­ marily affects the respiratory and digestive ferent ways and to varying degrees. systems in children and young adults. The However, the basic problem is the same— sweat glands and the reproductive system an abnormality in the glands, which pro­ are also usually involved. On the average, duce or secrete sweat and mucus. Sweat individuals with CF have a lifespan of cools the body; mucus lubricates the respi­ approximately 30 years. ratory, digestive, and reproductive systems, and prevents tissues from drying out, pro­ CF-like disease has been known for over tecting them from infection. two centuries. The name, cystic fibrosis of the pancreas, was first applied to the disease People with CF lose excessive amounts of in 1938. salt when they sweat. This can upset the balance of minerals in the blood, which may How Common Is CF? cause abnormal heart rhythms. Going into shock is also a risk. According to the data collected by the Cystic Fibrosis Foundation, there are about Mucus in CF patients is very thick and 30,000 Americans, 3,000 Canadians, and accumulates in the intestines and lungs. 20,000 Europeans with CF. The disease The result is malnutrition, poor growth, occurs mostly in whites whose ancestors frequent respiratory infections, breathing came from northern Europe, although it difficulties, and eventually permanent lung affects all races and ethnic groups. damage. Lung disease is the usual cause of Accordingly, it is less common in African death in most patients. Americans, Native Americans, and Asian CF can cause various other medical prob­ Americans. Approximately 2,500 babies are lems. These include sinusitis (inflammation born with CF each year in the United of the nasal sinuses, which are cavities in States. Also, about 1 in every 20 the skull behind, above, and on both sides Americans is an unaffected carrier of an of the nose), nasal polyps (fleshy growths abnormal “CF gene.” These 12 million inside the nose), clubbing (rounding and people are usually unaware that they are enlargement of fingers and toes), pneu­ carriers. mothorax (rupture of lung tissue and trap- NATIONAL INSTITUTES OF HEALTH NATIONAL HEART, LUNG, AND BLOOD INSTITUTE cf_new3.qxd 2/21/96 3:15 PM Page 2 ping of air between the lung and the chest wall), hemoptysis (coughing of CYSTIC FIBROSIS GENE blood), cor pulmonale (enlargement of the right side of the heart), AUTOSOMAL RECESSIVE INHERITANCE abdominal pain and discomfort, gassiness (too much gas in the intes­ Carrier Father Carrier Mother tine), 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. When Should You Suspect That a Child May Have CF? CF symptoms vary from child to child. A baby born with the CF genes usually has symptoms during Gg Gg 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 GG Gg Gg gg diarrhea, bulky foul-smelling and greasy stools, frequent wheezing or pneumonia, a chronic cough with thick mucus, salty-tasting skin, or poor growth. CF should be suspect­ ed in babies born with an intestinal blockage called meconium ileus. How Is CF Diagnosed? Normal Carrier Carrier Affected The most common test for CF is called the sweat test. It measures the amount of salt (sodium chloride) in The presence of two mutant genes (g) is needed for CF to appear. Each parent the sweat. In this test, an area of the carries one defective gene (g) and one normal gene (G). The single normal skin (usually the forearm) is made to gene is sufficient for normal function of the mucus glands, and the parents are sweat by using a chemical called therefore CF-free. Each child has a 25 percent risk of inheriting two defective pilocarpine and applying a mild elec­ genes and getting CF, a 25 percent chance of inheriting two normal genes, tric current. To collect the sweat, the and a 50 percent chance of being an unaffected carrier like the parents. 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 2 cf_new3.qxd 2/21/96 3:15 PM Page 3 chloride suggest that the person has can cause the body to make a defec­ for the basic causes of CF, although cystic fibrosis. tive protein or no protein at all. The several drug-based approaches are result is a loss of some essential bio­ being investigated. In the mean­ The sweat test may not work well in logical function and that leads to time, the best that doctors can do is newborns because they do not pro­ disease. Children may inherit altered to ease the symptoms of CF or slow duce enough sweat. In that case, genes from one or both parents. the progress of the disease so the another type of test, such as the patient’s quality of life is improved. immunoreactive trypsinogen test Diseases such as CF that are caused This is achieved by antibiotic thera­ (IRT), may be used. In the IRT test, by inherited genes are called genetic py combined with treatments to blood drawn 2 to 3 days after birth diseases. In CF, each parent carries clear the thick mucus from the is analyzed for a specific protein one abnormal CF gene and one nor­ lungs. The therapy is tailored to the called trypsinogen. Positive IRT mal CF gene but shows no evidence needs of each patient. For patients tests must be confirmed by sweat of the disease because the normal CF whose disease is very advanced, lung and other tests. gene dominates or “recesses” the transplantation may be an option. abnormal CF gene. To have CF, a Also, a small percentage of people child must inherit two abnormal CF was once always fatal in child­ with CF have normal sweat chloride genes—one from each parent. The hood. Better treatment methods levels. They can only be diagnosed recessive CF gene can occur in both developed over the past 20 years by chemical tests for the presence of boys and girls because it is located have increased the average lifespan the mutated gene. Some of the on non-sex-linked chromosomes of CF patients to nearly 30 years. other tests that can assist in the called autosomal chromosomes. CF These treatment approaches are diagnosis of CF are chest x-rays, is therefore called an autosomal detailed more fully below: lung function tests, and sputum recessive genetic disease. (phlegm) cultures. Stool examina­ ■ Management of lung problems tions can help identify the digestive The inheritance patterns for the CF A major focus of CF treatment is the abnormalities that are typical of CF. gene are shown in the accompany­ obstructed breathing that causes ing diagram. Each child, whether frequent lung infections. Physical What Makes CF a Genetic male or female, has a 25 percent risk therapy, exercise, and medications Disease? of inheriting a defective gene from are used to reduce the mucus block­ each parent and of having CF. A Genes are the basic units of heredity. age of the lung’s airways. child born to two CF patients (an They are located on structures with­ unlikely event) would be at a 100 Chest therapy consists of bronchial, in the cell nucleus called chromo­ percent risk of developing CF. or postural, drainage, which is done somes. The function of most genes by placing the patient in a position is to instruct the cells to make par­ that allows drainage of the mucus ticular proteins, most of which have How Is CF Treated? from the lungs. At the same time, important life-sustaining roles. Since CF is a genetic disease, the the chest or back is clapped (per­ only way to prevent or cure it would Every human being has 46 chromo­ cussed) and vibrated to dislodge the be with gene therapy at an early somes, 23 inherited from each par­ mucus and help it move out of the age. Ideally, gene therapy could ent. Because each of the 23 pairs of airways. This process is repeated repair or replace the defective gene. chromosomes contains a complete over different parts of the chest and Another option for treatment would set of genes, every individual has back to loosen the mucus in differ­ be to give a person with CF the two sets (one from each parent) of ent areas of each lung. This proce­ active form of the protein product genes for each function. In some dure has to be done for children by that is scarce or missing. individuals, the basic building family members but older patients blocks of a gene (called base pairs) At present, neither gene therapy nor can learn to do it by themselves. are altered (mutated). A mutation any other kind of treatment exists Mechanical aids that help chest 3 cf_new3.qxd 2/21/96 3:15 PM Page 4 physical therapy are available com­ treat the gene abnormality that mercially. Exercise also helps to causes CF.