This information is intended to help families who may be affected by cystic fibrosis (CF) better understand this disorder, including the advantages and disadvantages of existing and new treatment options. You will also find listings of other valuable informational resources, medical facilities staffed by specialists in the treatment of cystic fibrosis, and local family support organizations.
What Is CF?
What Causes CF?
What Parts of the Body Are Affected?
What Are the Symptoms of CF?
Who Develops CF?
Diagnosis
Treatment
Pancreatic Enzyme Replacement Therapy
Glossary
What Is CF?
CF is a genetic (inherited) disorder in which mucus secretions become abnormally thick. Mucus serves an important role in the human body: it lubricates the respiratory, digestive, and reproductive systems, and prevents tissues from drying out, protecting them from infection. The thick and sticky mucus of CF hampers the normal functioning of these bodily systems.
What Causes CF?
CF is caused by a genetic defect. Under normal circumstances, a particular gene controls the flow of salt (sodium chloride) and water in cells that produce mucus. Normally, mucus is thin and watery, allowing it to efficiently cleanse and lubricate bodily tissues. In contrast, in a CF individual, the mucus contains too little water and it becomes thick, moving only sluggishly and blocking critical passageways.
What Parts of the Body Are Affected?
CF typically affects glands and organs of the digestive tract, the respiratory system, and the reproductive system. The sweat glands are also commonly affected.
Digestive system. CF can have serious effects on the digestive system, primarily due to the clogging of ducts within the pancreas by thick, sticky mucus which then blocks the release of pancreatic enzymes into the duodenum. This results in inadequate absorption of nutrients. Scar tissue may develop within the pancreas, causing complete blockage of its secretions. In some individuals, ducts leading from the liver may also become blocked.
Respiratory system. Thick mucus can clog the airways in CF patients. This not only reduces breathing efficiency, but makes individuals more susceptible to infection and leads to chronic and progressive inflammation and scarring of lung and airway tissues.
Reproductive organs. In males, the vas deferens, the tube that carries sperm from the testes to the penis, may not develop properly or may become blocked. In females, the mucus secreted by the cervix may be abnormally thick. This can cause infertility in males although pregnancy is usually possible for females with CF.
Sweat glands. Because of impaired salt absorption, the sweat glands of people with cystic fibrosis commonly secrete an excessive amount of salt. In some individuals, the salivary glands may be similarly affected.
What Are the Symptoms of CF?
The symptoms of CF and their severity vary from person to person. This is due to each individual's genetic makeup, subtle differences in the gene defects occurring among people with the disorder, or other causes that are not yet known. Common symptoms are described below.
Gastrointestinal symptoms. Symptoms that involve the digestive system, or gastrointestinal (GI) tract, are very common in people with CF. In some individuals, damage to the pancreas begins prior to birth. Since pancreatic enzymes are lacking, nutrients cannot be absorbed properly. As a result, malnutrition may occur and normal growth may be hindered in some children with CF. This compromises the body's natural defenses, which puts patients with CF at greater risk of developing serious pulmonary complications. Other less frequent effects include gallstones and liver impairment. Newborn babies with CF may have meconium ileus and meconium plug syndrome, obstructions of the intestinal tract that may require surgery.
Respiratory symptoms. Typically, respiratory problems develop later than GI symptoms. The most common pulmonary symptoms of CF are chronic wheezing and cough, sometimes accompanied by the expulsion of mucus. Coughing may be accompanied by gagging and vomiting. The sticky mucus in the airways leads to frequent and chronic respiratory tract infections. Cycles of infection and inflammation in the lungs ultimately cause irreparable damage.
Salty perspiration. People with CF have perspiration that is much saltier than that of people who do not have CF.
Diabetes. In addition to the digestion of food, the pancreas produces and secretes the hormone insulin, which regulates how the body's cells use glucose for fuel. CF may also impair insulin secretion, although usually only in adults with CF.
Infertility. Nearly all males with CF can have some degree of infertility. Although women with CF often find it difficult to become pregnant, the majority can bear children.
Who Develops CF?
Approximately 30,000 children and adults in the United States have CF. CF is passed on to children genetically. Although parents may not have CF themselves, they may be carriers of CF, meaning they have one defective CF copy and one normal copy of the gene. CF occurs in babies who inherit two defective copies of this gene, one from each parent. If both parents are carriers, each of their children has a 25% chance of developing CF (inheriting two defective copies of the gene), a 50% chance of being a carrier but not developing CF (inheriting one defective copy of the gene), and a 25% chance of having completely normal genes. The odds of having a baby with CF increase dramatically if one parent has CF. If the other parent is a CF carrier, each child has a 50% chance of inheriting the disease and a 50% chance of being a carrier. If a man with CF and a woman with CF were able to have a child, the odds of CF occurring in the child would be 100%.
It is thought that the defect is in a gene responsible for production of a protein called the cystic fibrosis transmembrane regulator (CFTR). Due to this defect, the CFTR protein that the gene produces cannot regulate the flow of salt (sodium chloride) and water to and from mucus-producing cells, causing mucus to become heavy and sticky.
Diagnosis
Neonatal screening. Today, babies born in many US hospitals are routinely screened for the presence of CF. The method of screening is the IRT, or immunoreactive trypsinogen test. A small amount of blood is collected and analyzed for the presence of trypsinogen, a protein produced by the pancreas. An elevated level of this protein suggests the presence of CF. If a second test is also positive, a sweat test is performed to confirm the diagnosis.
Sweat test. A sweat test is a simple procedure used to determine the amount of salt in an individual's perspiration. A medication to cause sweating is applied directly to a small area of the arm or leg, after which mild and painless electric current is applied for approximately 5 minutes. The perspiration is collected directly from the skin and sent to a laboratory to be analyzed. When performed and evaluated by trained, experienced technicians, and when strict procedural guidelines are followed, the sweat test is the most reliable diagnostic tool for the detection of CF. In addition, this test can have false-negative results in newborns and others, sometimes due to less pronounced gene mutations, so it may be considered controversial.
Genetic testing. A person may also be diagnosed as having CF or as being a carrier of CF through genetic screening, in which the genes in a small sample of blood or tissue are analyzed for specific defects. Prenatal testing via amniocentesis or chorionic villus sampling is also possible. Although genetic testing for CF can be highly accurate, its usefulness is limited.
Treatment
There is not yet a cure for CF. However, the outlook for people with CF has improved dramatically over the past few decades. With early diagnosis and treatment, individuals with the disease can now live longer and richer lives than ever before. Today, people with CF have a median lifespan of about 37 years.
The primary goals of treatment are to maintain adequate nutrition, prevent and control infections, and promote clearance of mucus from the airways. Specific treatment guidelines depend on the unique needs of the individual. A team of health- and social-service professionals, including physicians, nurses, nutritionists, respiratory therapists, pharmacists, and counselors, will work with patients and their families on an ongoing basis to ensure that individual needs are met.
Nutrition. Proper nutrition is a vital component in the treatment of CF patients. It helps ensure proper growth and quality of life, and is an important contributor to pulmonary health.
Most people with CF require well-balanced, high-calorie diets along with supplements of vitamins A, D, E, and K. Individuals with CF may need to consume up to one third more food than people without CF. Most patients also need to take pancreatic enzymes with every meal and snack (see below for more detailed discussion) to replace or supplement the natural enzymes that are lost. In some cases, people with CF may also require supplemental nutrition administered intravenously or through a feeding tube.
Pulmonary health. The major objectives of CF treatment are to improve impaired breathing and control lung infections. Depending on individual needs, approaches to pulmonary health may include physical therapy, exercise, and medications.
Chest therapy is often performed to clear mucus from the lungs: Bronchial drainage (also known as percussion or postural drainage) entails placing the person with CF in a downward-tilted position while his or her chest or back is manually thumped or vibrated with a mechanical device to loosen mucus and help it drain out of the airways. Aerobic exercise may also help both dislodge mucus and maintain optimal lung function. Among the various medications used to improve breathing in people with CF are bronchodilators, mucolytic agents, and decongestants. Many patients additionally use corticosteroids to reduce lung inflammation. The use of antibiotics to prevent or treat lung infections is common; these may be administered orally, in aerosol form, or by injection. Immunization against common respiratory tract infections such as influenza is frequently recommended.
Pancreatic Enzyme Replacement Therapy
Pancreatic enzyme replacement therapy (PERT) is an essential component in the treatment of most people who are afflicted with CF. It supplements the critical digestive enzymes that are lost to CF, aiding absorption of nutrients from food.
Normal digestion. The human digestive system extends from the mouth to the rectum. It consists of the alimentary canal (mouth, esophagus, stomach, small intestine, and large intestine) as well as the pancreas and the liver. It functions to digest food, breaking it down into elemental components of fat, protein, and carbohydrates that can be absorbed into the bloodstream and utilized for growth and energy.
The majority of digestive processes occur in the small intestine, facilitated by enzymes secreted from the pancreas. There are 3 major enzyme types that the pancreas secretes, each having a specific function:
- lipases, which digests fats
- proteases, which digests proteins
- amylases, which digests starch and other carbohydrates.
Together, these enzymes are able to reduce virtually all digestible foods into forms the body can use as energy.
Pancreatic insufficiency. A major consequence of CF and chronic pancreatitis is pancreatic insufficiency, where the ability of the pancreas to generate and secrete these enzymes to the intestine for digestion is decreased or eliminated entirely. Pancreatic insufficiency results in malabsorption of nutrients which can cause malnutrition, poor weight gain, and impaired growth in affected people, even though they might still be eating as much as, or more than, they should. These people are often at increased risk for infections of the lungs because their immune system may not be operating as it should. The most effective way to treat pancreatic insufficiency is through PERT.
PERT is a life-saving treatment involving administration of pancreatic enzymes. Currently available PERT regimens were developed by extracting enzymes from the pancreas of the pig. The aim of PERT is to improve nutritional status and bowel-related symptoms, as well as relieve abdominal pain in people with pancreatic insufficiency, such as that occurring in CF. At present, PERT products are generally enteric-coated, a process that is supposed to keep them from denaturing until they reach the low-acid environment of the small intestine. In spite of this, many patients using PERT are advised to also take additional medications that reduce the levels of stomach acid, ensuring that the benefit of PERT is gained. Polymer coatings hinder the enzymes' ability to be effective in the important areas of the GI tract. Currently available PERTs have been documented to have poor stability and wide variety in treatment effect.
Typically, PERT is administered with every meal and snack. Although it is individualized according to need, the per meal dosage of PERT is high, usually 4 to 5 large capsules, which increases the risk of insufficient dosing.
Glossary
Antibiotic
A medication that kills bacteria (germs), used to fight infection
Amniocentesis
A medical procedure in which a sample of amniotic fluid (the fluid surrounding an unborn baby) is removed from the uterus using a needle and sent to a laboratory for evaluation
Bronchodilator
A medication used to open the airways
Carbohydrate
A major classification of foods that includes all sugars and starches
Chorionic villus sampling
A medical procedure in which a small sample of the placenta (tissue providing nourishment for an unborn baby) is taken from the uterus and sent to a laboratory for evaluation
Decongestant
A medication used to reduce swelling in the membranes of the airways
Digestive System
The system by which ingested food is acted upon by physical and chemical means to provide the body with absorbable nutrients and to excrete waste products. The system includes the alimentary canal, extending from the mouth to the anus, and the hormones and enzymes assisting in digestion.
Duodenum
The first section of the small intestine where digestion takes place
Enzymes
Proteins produced by living cells that help facilitate chemical reactions such as digestion
Fat
A major classification of foods that includes the fats found in meat, dairy products, cooking oils, etc.
Gallstones
Abnormal solids that form in the gallbladder
Gastrointestinal (GI) Tract
The part of the digestive system containing the stomach and intestines, the most important organs for nutrient digestion and absorption
Gene
The basic element of hereditary sequences of DNA that are passed from parents to children Genes serve as the "blueprints" for the makeup and the functioning of the human body.
Gland
A specialized bodily structure that secretes hormones, mucus, enzymes, and other substances
Inflammation
The body's response to injury or infection Inflammation may result in pain, swelling, and damage to the affected body part.
Liver
The large organ in the abdomen with a variety of critical roles, including filtering toxins from the blood, producing important components of the blood, and regulating utilization of food for fuel
Meconium
The first feces (stool) of a newborn baby
Meconium Ileus
An obstruction of the intestine, or ileus, due to overly thick meconium resulting from a pancreatic enzyme deficiency
Meconium Plug Syndrome
A failure to pass the meconium which causes abdominal distension and vomiting
Mucus
The watery and slimy material produced by specific cells that line the inside passageways of the body, functioning to lubricate and protect them
Mucolytic
A medication used to thin the mucus
Organ
A bodily structure containing specific types of tissues organized to perform a specific function. Examples include the brain, lungs, heart, and kidneys
Pancreas
A gland that secretes digestive enzymes, insulin, and other substances
Pancreatic enzymes
Proteins secreted by the pancreas that flow into the small intestine, where they help digest food
Protein
A major classification of food, found in meats, fish, beans, and other sources, OR a complex organic compound made of amino acids that is main component of muscles, organs, and glands
Pulmonary
Involving the lungs
Reproductive system
The organs and glands involved in sex and reproduction
Respiratory system
The system by which oxygen is taken into the body to be exchanged for carbon dioxide. It includes the nasal passages, the pharynx, trachea, bronchi, and lungs
