Cystic fibrosis is a genetic disorder that often affects multiple organ systems of the body. Cystic fibrosis is characterized by abnormalities affecting certain glands (exocrine) of the body especially those that produce mucus. Saliva and sweat glands may also be affected. Exocrine glands secrete substances through ducts, either internally (e.g., glands in the lungs) or externally (e.g., sweat glands). In cystic fibrosis, these secretions become abnormally thick and can clog up vital areas of the body causing inflammation, obstruction and infection. The symptoms of cystic fibrosis can vary greatly in number and severity from one individual to another. Common symptoms include breathing (respiratory) abnormalities including a persistent cough, shortness of breath and lung infections; obstruction of the pancreas, which prevents digestive enzymes from reaching the intestines to help break down food and may result in poor growth and poor nutrition; and obstruction of the intestines. Cystic fibrosis is slowly progressive and often causes chronic lung damage, which eventually results in life-threatening complications. Because of improved treatments and new treatment options, the outlook and overall quality of life of individuals with cystic fibrosis has improved and more than 40 percent of individuals with the disorder are adults. Cystic fibrosis is caused by mutations to the CFTR gene and is inherited as an autosomal recessive trait
The symptoms of cystic fibrosis result because mucus secretions, which are normally thin and slippery and serve as a protective lubricant, are abnormally thick and sticky. Other secreted material such as saliva, sweat and digestive juices may also be affected. These abnormal secretions can clog up vital tubes, ducts and passageways throughout the body.
Multiple organ systems may be affected by cystic fibrosis, especially the lungs and pancreas. The intestines, liver, sweat glands and reproductive organs are also frequently affected. The symptoms of cystic fibrosis can vary greatly from one individual to another. Some individuals may only have respiratory problems without other complications. Some individuals may only have a few mild symptoms; others may have serious complications. The severity of specific symptoms also varies. Some individuals may have mild respiratory complications, while others may have serious, life-threatening respiratory complications early during life. Affected individuals will not have all the symptoms discussed below.
Cystic fibrosis is often apparent shortly after birth, but when symptoms are not severe it may not be detected until years later or, in rare cases, even until adulthood. Most cases diagnosed in adulthood have no associated symptoms (asymptomatic) or only very mild symptoms.
Affected individuals develop a variety of breathing (respiratory) complications due to the production of thick, sticky mucus that clogs various air passages in the body. Associated symptoms include a persistent cough that often produces mucous or phlegm (productive cough), wheezing, and shortness of breath. Because mucus clogs the airways, bacteria become trapped and accumulate within the lungs and air passages making individuals particularly prone to developing repeated (chronic) respiratory infections such as inflammation of the main air passages of the lungs (bronchitis), inflammation of the sinuses (sinusitis) and inflammation of the lungs (pneumonia). Clogging of the airways with mucous may also make it difficult to breath.
The immune system of individuals with cystic fibrosis responds to an infection by sending white blood cells to attack the infection. After attacking the infection, white blood cells breakdown and further clog the airways. The repeated cycle of infection and immune system response slowly and progressively damages the lungs, which can develop holes or depressions (cysts) and accumulate scar tissue (fibrosis). Chronic mucus blockage and infection of the respiratory passageways may cause them to become abnormally widened (bronchiestasis), which permits more mucus to build up and further increase the risk of infection. Eventually, continued damage to the lungs can cause life-threatening respiratory failure or enlargement and improper function of the lower right chamber (ventricle) of the heart (cor pulmonale). Enlargement of the ventricle occurs because the heart must work harder to try and pump blood through the damaged lungs.
In many cases, cystic fibrosis may cause pancreatic insufficiency. The pancreas is a small organ located behind the stomach that secretes enzymes that travel to the intestines and aid in digestion. The pancreas also secretes other hormones such as insulin, which helps break down sugar. When mucous builds up in the pancreatic ducts, it may block the enzymes from reaching the intestines and helping the breakdown and absorption of food and nutrients. Failure of the body to breakdown and absorb nutrients is called malabsorption and can potentially result in a variety of nutritional deficiencies in affected individuals. In childhood, it may result in failure of an affected child to grow and gain weight at the expected rate for age and sex (failure to thrive). Affected individuals may also have large, loose, foul-smelling stools that contain and excess of fat (steatorrhea) and other nutrients due to malabsorption.
The first symptom in cases diagnosed during infancy is often meconium ileus – obstruction of the intestines with a thick, tarry substance called meconium. Meconium is the medical term for an infant's first stool, which is passed shortly after birth.
Mucus may also build up in the sweat ducts and can prevent the absorption of salt resulting in higher than normal levels of salt in the sweat. Salt depletion may upset the balance of minerals in the body, causing abnormal heart rhythms or the body to overheat.
Mucus can also accumulated within the small tubes that carry bile from the liver to the intestines (bile ducts) causing obstruction and inflammation. In some cases, high blood pressure of the major vein that carries blood to the liver from the digestive organs may occur (portal hypertension). Obstruction of the bile ducts can damage the liver, eventually leading to scarring of the liver (cirrhosis). Damage to the liver can potentially become life-threatening.
Some boys with cystic fibrosis may be born without the small tubes that carry sperm out from the testes (congenital absence of the vas deferens) resulting in infertility. In other cases, male infertility may be caused by underdevelopment (atrophy) or damage (fibrosis) of the vas deferens. In some girls, fertility may be reduced due to the accumulation of abnormal mucus in the cervix and irregular menstrual periods.
Additional respiratory symptoms may be associated with cystic fibrosis including the development of small growths in the nose (nasal polyps), rounding or flattening (clubbing) of the tips of the fingers or toes, coughing up of blood (hemoptysis), recurrent episodes of lung collapse (pneumothorax), and abnormally fast breathing (tachypnea).
Additional gastrointestinal symptoms associated with cystic fibrosis may occur including recurrent abdominal pain, bloating (distention) of the abdomen, backflow of the contents of the stomach into the tube (esophagus) that connects the back of the mouth to the stomach (gastroesophageal reflux) and protrusion of part of the rectum through the anus (rectal prolapse). In some cases, the gall bladder may be filled with thick, sticky mucus and fail to function properly. The gall bladder is a small, pear-shaped organ located under the liver that stores bile. Some individuals may develop gall stones.
Individuals with cystic fibrosis may be at risk for developing cystic fibrosis-related diabetes mellitus (CFRD). CFRD may occur in some adolescents with cystic fibrosis, although the prevalence increases during adulthood. The onset of CFRD is slow and individuals may not have symptoms (asymptomatic). CFRD develops due to damage to the pancreas (which limits insulin production) and increased resistance to insulin. CFRD can also worsen lung function in affected individuals.
Another specific condition that may develop in individuals with cystic fibrosis is known as distal intestinal obstruction syndrome, in which food and mucus clog the intestines. This condition can cause stomach aches, bloating, cramping, nausea and loss of appetite. In severe cases, it may cause pain, vomiting and watery stools. The incidence of distal intestinal obstruction syndrome appears to increase with age; most cases tend to occur in adolescents and adults.
Cystic fibrosis is caused by mutations of the cystic fibrosis transmembrane conductance regulator (CFTR) gene. This defective gene is inherited as an autosomal recessive trait. Genetic diseases are determined by the combination of genes for a particular trait that are on the chromosomes received from the father and the mother.
Recessive genetic disorders occur when an individual inherits the same abnormal gene for the same trait from each parent. If an individual receives one normal gene and one gene for the disease, the person will be a carrier for the disease, but usually will not show symptoms. The risk for two carrier parents to both pass the defective gene and, therefore, have an affected child is 25 percent with each pregnancy. The risk to have a child who is a carrier like the parents is 50 percent with each pregnancy. The chance for a child to receive normal genes from both parents and be genetically normal for that particular trait is 25 percent. The risk is the same for males and females.
Investigators have determined that the CFTR gene is located on the long arm (q) of chromosome 7 (7q31.2). Chromosomes, which are present in the nucleus of human cells, carry the genetic information for each individual. Human body cells normally have 46 chromosomes. Pairs of human chromosomes are numbered from 1 through 22 and the sex chromosomes are designated X and Y. Males have one X and one Y chromosome and females have two X chromosomes. Each chromosome has a short arm designated "p" and a long arm designated "q". Chromosomes are further sub-divided into many bands that are numbered. For example, "chromosome 7q31.2" refers to band 31.2 on the long arm of chromosome 7. The numbered bands specify the location of the thousands of genes that are present on each chromosome.
The CFTR gene is primarily expressed in cells lining the airways, gastrointestinal tract, pancreas, sweat glands, and genitourinary system. The gene controls the production of a protein that regulates the transfer of chloride and sodium across cell membranes. Accordingly, investigators speculate that inheritance of the defective CFTR gene results in disruption of chloride and sodium transfer, ultimately leading to low levels of certain bodily fluids (dehydration), abnormally thick mucus and other glandular secretions, salt loss, and impaired glandular functioning.
Cystic fibrosis affects males and females in equal numbers. Approximately 30,000 people have cystic fibrosis in the United States. One thousand new cases are diagnosed each year. The disorder occurs predominately among Caucasians, occurring in approximately one of every 3,200 live Caucasian births compared to one in 3,900 live births of all Americans. Among African Americans, CF is manifest in about one in 15-17,000 live births. There is also a small but significant number of Americans of Asian descent who are affected by the disorder. Most individuals are diagnosed by age three. . In many cases, this disorder is apparent soon after birth, but 10 percent of the people with cystic fibrosis do not receive a diagnosis until age 18 or older. According to the Cystic Fibrosis Foundation, more than 12 million Americans are symptomless carriers of the defective cystic fibrosis gene. Cystic fibrosis is the most common, life-limiting recessive genetic disorder in Caucasians.
Symptoms of the following disorders can be similar to those of cystic fibrosis. Comparisons may be useful for a differential diagnosis.
Primary ciliary dyskinesia (PCD) is rare disorder involving the tiny, hair-structures that cover many cells of the body. Cilia in the respiratory passageways help to move mucus out of these passageways. In individuals with PCD, the cilia are defective allowing mucus to build up in the airways and respiratory passageways of the body. Symptoms may include inflammation of the sinuses (sinusitis), repeated respiratory infections, and pneumonia and can, consequently, cause progressive lung damage. PCD can also affect the middle ear and the reproductive organs. PCD is inherited as an autosomal recessive trait. (For more information on this disorder, choose "primary ciliary dyskinesia" as your search term in the Rare Disease Database.)
Shwachman syndrome is a rare genetic disorder with multiple and varied manifestations. The disorder is typically characterized by signs of insufficient absorption (malabsorption) of fats and other nutrients due to abnormal development of the pancreas (pancreatic insufficiency) and improper functioning of the bone marrow (bone marrow dysfunction), resulting in low levels of circulating blood cells (hematologic abnormalities). Additional characteristic findings may include short stature; abnormal bone development affecting the rib cage and/or bones in the arms and/or legs (metaphyseal dysostosis); and/or liver abnormalities. Due to abnormal skeletal changes, individuals with Shwachman syndrome may have abnormal thickening of the ribs and their supporting connective tissue (costochondral thickening), resulting in unusually short, flared ribs. In addition, improper bone development (abnormal ossification) within the arms and/or legs (limbs) may cause growth delay in particular bones. Many children with Shwachman syndrome may also be smaller than expected for their ages, with below average height (short stature) and weight. Although malabsorption due to pancreatic insufficiency may itself cause problems with growth and nutrition, short stature appears to be one of the many primary manifestations of Shwachman syndrome. In addition, as a result of bone marrow dysfunction, individuals with Shwachman syndrome may have a decrease in any or all types of blood cells. Therefore, they may have low levels of certain white blood cells (neutropenia), platelets (thrombocytopenia), red blood cells (anemia), and/or all types of blood cells (pancytopenia). Neutropenia is the most common blood abnormality associated with Shwachman syndrome. Because neutrophils, a type of white blood cell, play an essential role in fighting bacterial infections, many affected individuals are prone to repeated bacterial infections (e.g., recurrent respiratory infections [pneumonia] and infections of the middle ear [otitis media]); in some cases, infections may be severe. Some affected individuals may also have abnormal enlargement of the liver (hepatomegaly), increased levels of certain liver enzymes in the blood, and/or other findings in association with the disorder. Shwachman syndrome is believed to be inherited as an autosomal recessive trait. (For more information on this disorder, choose "Shwachman" as your search term in the Rare Disease Database.)
Diagnosis A diagnosis of cystic fibrosis may be suspected based upon identification of characteristic symptoms (e.g., pulmonary disease, pancreatic insufficiency) or a positive family history. The standard diagnostic test for cystic fibrosis is the sweat test, a painless and simple procedure that measures the amount of salt in the sweat. Genetic testing can identify carriers of the defective gene. In May 2005, the U.S. Food and Drug Administration (FDA) approved the first DNA-based blood test to help detect cystic fibrosis. The Tag-It Cystic Fibrosis Kit directly analyzes human DNA to find genetic variations indicative of the disease.
Newborn screening: It is recommended for all newborns to be screened for cystic fibrosis. Although it is not a definitive test, it does help in ruling it out and/or for confirmation of the diagnosis.
On September 4th, 2009 a biological testing equipment company Luminex Corp. has received clearance from the U.S. Food and Drug Administration for a new cystic fibrosis test.
Treatment There is at present no cure for cystic fibrosis. Treatment depends upon the stage of the disease and the specific organs that are involved. Treatment is geared toward reducing the thickness and amount of mucus in the airways, preventing infections, preventing blockage of the intestines and ensuring the proper intake of vitamins and nutrients.
Various forms of chest physical therapy, such as applying cupped hands vigorously to the back and chest, may help to dislodge thick mucus from the lungs and maintain clear airways. Some physical therapy techniques require assistance from family members or friends; others can be performed by adults with cystic fibrosis without aid. In some cases, devices such as a mechanical vest may be used to help clear airways. This inflatable vest creates vibrations (high-frequency air waves) that loosen mucus in the chest. Other devices require affected individuals to blow into a tube, which helps loosen and dislodge mucus.
Antibiotics may be used to treat lung infections. In addition, inhaling particular medications via nebulizers may help to wet and thin the mucus secretions. The antibiotic drug tobramycin solution for inhalation (TOBI®) has been approved by the FDA for the treatment of bronchopulmonary infections of Pseudomonas aeruginosa (the most common source of chronic lung infection) in individuals with cystic fibrosis. It is manufactured by Chiron.
When the gastrointestinal system is involved, affected individuals may need to eat an enriched diet and/or take replacement vitamins, especially vitamins A, D, E and K. Also, studies have shown that neonatal screening may provide an opportunity to prevent malnutrition in infants with cystic fibrosis. Pancreatic insufficiency may be treated by enzyme replacement therapy and diet.
The drug dornase alfa (Pulmozyme®) inhalation solution was approved by the FDA for the treatment of CF in 1993. It was the first new drug therapy to be developed exclusively for CF in 30 years. In clinical trials, this mucus-thinning drug reduced the rate of respiratory infection and improved pulmonary function. FDA approval is limited to those over the age of five years. Pulmozyme is a mucolytic, a drug designed to help thin, loosen and clear mucus, and is manufactured by Genentech, Inc.
Medications that widen the bronchial tubes and aid in the clearing of mucus (bronchodilators) may be used in some cases. Albuterol is an example of a bronchodilator. Ibuprofen has been show to slow the rate of lung function decline in individuals with cystic fibrosis. Treatment of individuals with cystic fibrosis with hypertonic saline (sterilized, extra-salty water) has shown better mucus clearance and improved lung function.
In severe cases of cystic fibrosis, a lung transplant may be necessary. A decision concerning the use of a lung transplant is made by physicians and other members of the health care team in careful consultation with the patient, based upon the specifics of his or her case; a thorough discussion of the potential benefits and risks; patient preference; and other appropriate factors.
Genetic counseling may be of benefit for affected individuals and their families. Other treatment is symptomatic and supportive.
Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. Government funding, and some supported by private industry, are posted on this government web site.
For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:
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March of Dimes Birth Defects Foundation 1275 Mamaroneck Avenue White Plains, NY 10605 Tel: (914)428-7100 Fax: (914)997-4763 Tel: (888)663-4637 Email: Askus@marchofdimes.com Internet: http://www.marchofdimes.com
American Lung Association 61 Broadway, 6th Floor New York, NY 10006 USA Tel: (212)315-8700 Fax: (212)315-8870 Tel: (800)586-4872 Internet: http://www.lungusa.org
Canadian Cystic Fibrosis Foundation 2221 Yonge Street Suite 601 Toronto Ontario, Intl M1B 4G8 Canada Tel: (416) 485-9149 Fax: (416) 485-0960 Tel: (800) 378-2233 Email: info@cysticfibrosis.ca Internet: http://www.cysticfibrosis.ca
Cystic Fibrosis Trust Alexandria House 11 London Rd Bromley Kent, BR11BY UK Tel: 020 8646 7 Fax: 020 8313 0462 Email: enquiries@cftrust.org.uk Internet: http://www.cftrust.org.uk
NIH/National Digestive Diseases Information Clearinghouse 2 Information Way Bethesda, MD 20892-3570 Tel: (301)654-3810 Fax: (301)907-8906 Tel: (800)891-5389 Email: nddic@info.niddk.nih.gov Internet: http://www.niddk.nih.gov
Cochrane Cystic Fibrosis and Genetic Disorders Review Group Institute of Child Health Royal Liverpool Children's NHS Trust Alder Hey Hospital, Eaton Road Liverpool, L12 2 AP United Kingdom Tel: +44 (0) 1512525696 Fax: +44 (0) 1512525456 Email: cfgd@liv.ac.uk Internet: http://www.liv.ac.uk/cfgd/
MUMS (Mothers United for Moral Support, Inc) National Parent-to-Parent Network 150 Custer Court Green Bay, WI 54301-1243 USA Tel: (920)336-5333 Fax: (920)339-0995 Tel: (877)336-5333 Email: mums@netnet.net Internet: http://www.netnet.net/mums/
Genetic and Rare Diseases (GARD) Information Center PO Box 8126 Gaithersburg, MD 20898-8126 Tel: (301)519-3194 Fax: (240)632-9164 Tel: (888)205-2311 TDD: (888)205-3223 Email: gardinfo@nih.gov Internet: http://www.genome.gov/10000409
Madisons Foundation PO Box 241956 Los Angeles, CA 90024 Tel: (310)264-0826 Fax: (310)264-4766 Email: getinfo@madisonsfoundation.org Internet: http://www.madisonsfoundation.org
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