Cystic Fibrosis - Centers for Disease Control
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FACTS ABOUT
Cystic Fibrosis
What Is Cystic Fibrosis What Are the Signs and Symptoms
of CF?
Cystic fibrosis (CF) is a chronic, progressive,
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-
N A T I O N A L I N S T I T U T E S O F H E A L T H
N A T I O N A L H E A R T , L U N G , A N D B L O O D I N S T I T U T Ecf_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
GG Gg Gg gg
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 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
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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
How Is CF Treated? that allows drainage of the mucus
ticular proteins, most of which have
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
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physical therapy are available com treat the gene abnormality that
mercially. Exercise also helps to causes CF. In the laboratory, scien
loosen the mucus, stimulate cough tists have been able to grow cells HOW DOES THE GENE MUTATION
ing to clear the mucus, and improve from the nasal passages of CF CAUSE CF?
the patient’s overall physical patients. By introducing the normal
condition. gene into these cells, researchers
corrected the cells’ chloride trans The CF gene was identified in 1989.
Medications used to help breathing Since then, a great deal has been learned
port abnormality. The chloride
are often aerosolized (misted) and about this gene and its protein product.
defect has also been corrected in
can be inhaled. These medicines The biochemical abnormality in CF
small regions in the nasal passages
include bronchodilators (which results from a mutation in a gene that
themselves by giving CF patients
widen the breathing tubes), produces a protein responsible for the
the normal gene in nose drops.
mucolytics (which thin the mucus), movement through the cell membranes
and decongestants (which reduce Scientists are still looking for of chloride ions (a component of sodium
swelling of the membranes of the answers to many questions about chloride, or common table salt). The
breathing tubes). A recent advance, gene therapy. Some of these ques protein is called CFTR—cystic fibrosis
approved by the Food and Drug tions are: How should the gene be transmembrane regulator.
Administration, is an inhaled packaged? What are the best ways
aerosolized enzyme that thins the to get the gene-containing package CFTR is present in cells that line the
mucus by digesting the cellular into the patient’s lungs? What will passageways of the lungs, pancreas,
material trapped in it. Antibiotics to the long-term results of this treat colon, and genitourinary tract. When
fight lung infections also are used ment be? Can the abnormal chloride this protein is abnormal, two of the
and may be taken orally or in transport be corrected in other parts hallmarks of CF result—blockage of the
aerosol form, or by injection into a of the body? How long will the cor movement of chloride ions and water in
vein. rection last? And, most importantly, the lung and other cells and secretion of
can gene therapy cure or prevent abnormal mucus.
■ Management of digestive
the lung disease in CF? The mutation involved in CF causes the
problems
deletion of three of the base pairs in the
The digestive problems in CF are Is It Possible to Detect CF in gene. This in turn, causes a loss in the
less serious and more easily man an Unborn Baby? CFTR protein of an amino acid (the
aged than those in the lungs. A building blocks of proteins). Because
Finding out whether a baby is likely
well-balanced, high-caloric diet, phenylalanine is located in position 508
to have CF is possible using prenatal
low in fat and high in protein, and of the protein chain, this mutant protein
genetic tests. However, the tests
pancreatic enzymes (which help is called DF508 CFTR.
cannot detect all of the CF gene
digestion) are often prescribed.
Supplements of vitamins A, D, E,
mutations. Also, because these tests However, DF508 CFTR accounts for only
are very expensive and have certain 70-80 percent of all CF cases. Various
and K are given to ensure good
risks to the mother, they are not other mutations—over 400 at the last
nutrition. Enemas and mucolytic
used for all pregnant women. If count—seem to be responsible for the
agents are used to treat intestinal
there is another child with CF in the remaining CF cases. Differences in
obstructions.
family, the expectant mother may disease patterns seen in individuals and
request a prenatal test to see if the families probably result from the
Gene Therapy—The Future of
fetus has CF genes from both par combined effects of the particular
CF Treatment?
ents, is a carrier for one gene, or is mutation and various, but still unknown,
Gene therapy for CF is not yet pos altogether free of the CF genes. factors in the CF patient and his or her
sible but impressive progress is environment.
There are two special prenatal tests
being made in developing ways to
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that can be done—either an amnio How Can Patients and Their although they may be less fertile
centesis or chorionic villus biopsy Families and Friends Be than women without CF.
will be performed. In amniocentesis, Helped To Cope with CF?
■ Patients and families should
cells from the fluid surrounding the CF education helps patients and work closely with doctors and other
baby in the mother’s womb (called their families face the physical and medical specialists to develop self-
the amniotic fluid) are tested to see emotional effects of the disease and management skills that can improve
if the CF genes common to the par encourages CF patients to lead their quality of life.
ents are present. In chorionic villus active, fulfilling lives. Educational
biopsy, cells from the tissue that will Above all, CF patients and their
programs and materials suitable for
eventually form the placenta are families should keep a positive atti
both patients of various ages and
tested for the CF gene. tude. Scientists continue to make
their parents are available from local
significant advances in understand
CF centers and from local chapters
Can CF Be Prevented? ing the genetic and physiological
of the CF Foundation.
disturbances in CF and in develop
At this time, preventing CF is not Patients and their families and ing new treatment approaches such
possible. In babies with two abnor friends should know that: as gene therapy. The outlook is
mal CF genes, the disease is already
■ CF parents should not feel guilty bright for further improvements in
present at birth in some organs,
or responsible for causing their the care of CF patients and even for
such as the pancreas and liver, but
child’s disease; they could not have the discovery of a cure.
develops only after birth in the
lungs. Someday, gene therapy may prevented it.
be used to prevent the lung disease ■ Parents should treat their chil
from developing. dren with CF as normally as possi
Yet, CF might be prevented in the ble. They shouldn’t be over-pro
future. Since CF occurs only when tective but should encourage them
both parents pass on a CF gene to a to be active and self-reliant.
child, it could be prevented by iden ■ Family and friends should
tifying all carriers of CF genes. remember that CF is not conta
Genetic counselors might then per gious; nobody can get it from a
suade couples who are carriers not patient.
to have children. However, as noted,
current tests can detect only some of ■ In families with CF, brothers, sis
the more than 400 gene mutations ters, and first cousins of the CF
and so the tests are only 80-85 per patient should be tested to see if
cent accurate. they carry a defective gene, especial
ly if they seem to have a chronic
Yet, progress in gene therapy and lung or digestive problem. Carriers
the realization that not all CF muta of the abnormal gene should get
tions are life-threatening should genetic counseling.
reassure couples. Potential parents
who carry the defective gene may ■ Individuals with CF have normal
choose to have children. sexual development and can expect
to have a normal sex life. However,
most, but not all, men are infertile
because of a mechanical blockage of
sperm and cannot have children.
Women with CF can have children,
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FOR MORE
INFORMATION
Additional information
about CF can be obtained
from the following
organizations:
National Heart, Lung, and
Blood Institute (NHLBI)
Information Center
P.O. Box 30105
Bethesda, MD 20824-0105
Telephone: 301-251-1222
The Cystic Fibrosis
Foundation
6931 Arlington Road, #200
Bethesda, MD 20814
Telephone: 301-951-4422
1- 800-344-4823
National Diabetes
Information Clearinghouse
1 Information Way
Bethesda, MD 20892-3560
Telephone: 301-654-3327
1-800-891-5388
U.S. DEPARTMENT OF
HEALTH AND HUMAN
SERVICES
Public Health Service
National Institutes of Health
National Heart, Lung, and
Blood Institute
NIH Publication No. 95-3650
6 November 1995You can also read
