About Cystic Fibrosis (CF)
Quick Navigation:
What is Cystic Fibrosis?
Cystic Fibrosis (CF) is a chronic, progressive, and frequently fatal genetic disease of the exocrine glands of the body. CF primarily affects the respiratory and digestive systems in children and young adults. The average lifespan of most CF patients is now approximately 32 years - this estimate is based on the average that 1/2 of all CF patients will reach age 32, while 1/2 of CF patients will die before reaching this median survival age.
Illnesses that are "CF-like" have been known for over two centuries. The name "Cystic Fibrosis of the pancreas" was first applied to the disease in 1938.
How common is CF?
According to data collected by the Cystic Fibrosis Foundation, there are approximately 30,000 Americans; 3,000 Canadians; and 20,000 Europeans with CF. The disease occurs mostly in the Caucasian race, 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. Every year there are somewhere close to 2,500 babies born with CF in the United States. Also, about 1 in 20 Americans are thought to be an unknowing carrier of an abnormal CF gene. These 12 million people are unaffected by the CF gene, and usually are unaware that this genetic mutation makes them a carrier of CF.
What are the signs and symptoms of CF?
Cystic Fibrosis does not follow the same pattern in all patients, but will affect each patient in different ways and to varying degrees. Although there are many patients that suffer from a "classical" presentation of CF, there are just as many diagnosed patients that do not follow this "textbook" description. No matter what the presentation - the basic problem in all CF cases is the same - an abnormality at the cellular level, affecting the glands that produce or secrete sweat and mucus. Seat cools the body, and mucus lubricates the respiratory, digestive, and reproductive systems. The defect caused by the genetic mutation in CF patients causes the individual to lose excessive amounts of salt when they sweat, upsetting the balance of sodium chloride in the body.
Because of this abnormality, the mucus in CF patients is very thick and accumulates in the lungs and the intestines. The result is poor nutrition, poor growth, frequent respiratory infections, breathing difficulties, and eventually permanent lung damage. The resulting lung damage is the leading cause of death in CF patients.
CF can cause various other medical problems. These include (but are not limited to): sinusitis, nasal polyps, clubbing (rounding and enlargement of fingers and toes), pneumothorax, hemoptysis, cor pulmonale, abdominal pain and discomfort, gassiness, and rectal prolapse. Liver disease, diabetes, inflammation of the pancreas, and gallstones also occur in some people with CF.
How is CF diagnosed?
The most common test for CF is the sweat test. The sweat test measures the amount of salt (sodium chloride) in the sweat. In this test, an area of skin, usually the forearm, is made to sweat by using a chemical called pilocarpine and applying a mild electrical 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 is analyzed. Higher than normal amounts of sodium and chloride suggest that the person has Cystic Fibrosis. Although often considered the "gold standard" in diagnosing CF, the sweat test is not foolproof. It may not work well in newborns, because they do not produce enough sweat.
In a newborn with a suspected case of CF, another type of testing may be used. In the immunoreactive trypsinogen test (IRT), blood is drawn from the infant 2 to 3 days after birth and is analyzed for a specific protein called trypsinogen. Positive IRT tests must later be confirmed by sweat tests and other methods.
In some genetic mutations of CF, the patient will present with a normal sweat test. In instances such as this, CF can only be diagnosed by chemical tests for the presence of the mutated gene. Some other tests that can be of assistance in the diagnosis of CF are chest x-rays, lung function tests, and sputum (phlegm) cultures.
What makes CF a genetic disease?
Genetics are the basic building blocks of life, functioning as the the passing of man's inheritance. They are located on the structures within the cell nucleus called chromosomes. The function of most genes are to instruct the cells to make particular proteins, which have important life-sustaining roles.
Every human being has 46 chromosomes, 23 inherited from each parent. Because each of the 23 pairs of chromosomes contains a complete set of genes, every individual has two sets of genes for each function. In some individuals the basic building blocks of a gene (called base pairs) are altered or mutated. A mutation can cause the body to make a defective protein or no protein at all. The result is a loss of some essential biological function, which leads to disease or impairment. Children may inherit altered genes from one or both parents.
Diseases such as CF that are caused by inherited genes are called genetic diseases. In CF, each parents carries on abnormal CF gene and one normal CF gene, but shows no evidence of the disease because the normal gene dominates. For a person to have CF, he or she must inherit the abnormal gene from each parent. The recessive CF gene can occur in both boys and girls because it is located on non-sex-linked chromosomes called autosomal chromosomes. CF is therefore called an autosomal recessive genetic disease.
The inheritance pattern for CF is based on a 1:4 ratio. Each child, whether male or female, stands a 25% percent chance of having CF, a 25% of being completely free of the genetic mutation for CF, and a 50% chance of being a carrier of the CF gene. A child born to two CF patients (an unlikely event) stands a 100% chance of being born with Cystic Fibrosis.
CF Research
The location of the defective CF gene was located in 1989, causing a drastic increase in the pace of CF research. In 1990, scientists successfully made copies of the normal gene, and added them to CF cells in laboratory dishes, which corrected the defective cells. The next major step was achieved in early 1993 when the first experimental gene therapy treatment was given to a patient with CF. Researchers modified a common cold virus to act as a delivery vehicle, carrying the corrected genes to the CF cells in the airways. Currently, several Foundation supported studies are underway to test new gene delivery methods, such as fat capsules (liposomes) and synthetic vectors.
The UAB CF Research Center has been nationally recognized as an active participant in the advancement of CF research!
When should I suspect that my child has CF?
CF symptoms vary from person to person. A baby born with the CF genes usually has symptoms during its first year - but this is not always the case. In some cases, signs of the disease may not present 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 mucus; salty-tasting skin; or poor growth. CF should also be suspected in infants that present with an intestinal blockage called meconium ileus.
For More Information:
Source: NHLBI: Facts about Cystic Fibrosis.