- A one in four (25%) chance that the child will have CF
- A two in four (50%) chance that the child will be a carrier
- A one in four (25%) chance that the child will not carry the CF gene
What Is CF?
Cystic Fibrosis (CF) is one of the most common genetic (inherited) diseases in America. It is also one of the most serious. It mainly affects the lungs and the digestive systems in the body, causing breathing problems and problems digesting foods. It is a chronic disease that currently has no cure.
What Happens?
Glands in the body that usually produce thin, slippery
secretions (like sweat, mucous, tears, saliva, or
digestive juices) produce thick, sticky secretions.
These thick, sticky secretions plug up the ducts
(small tubes) that should carry the secretions either
outside of the body or into a hollow organ such as the
lungs or the intestines. This can affect vital body
functions such as breathing or digestion.
Why?
CF is present at birth because both parents carried a CF gene,
and their infant inherited a CF gene from each parent. Not every child
from this family will necessarily have CF. Other children could inherit
a single CF gene from just one parent, and thus become a carrier for CF,
or they could inherit no CF gene and be completely free from CF.
Since 1989, when the CF gene was first discovered, research has made great
progress in understanding CF.
How is CF diagnosed?
A suspicion of CF occurs when some of these symptoms are present:
What is a gene?
A gene is the basic unit of heredity. Genes are responsible for the
physical characteristics that each person has (like eye color, facial
features, and many health conditions). Each gene occupies a certain
location on a chromosome (a thread-like material that is located in the
nucleus of every single cell in the body). Chromosomes come in 23 pairs,
and each chromosome carries thousands of genes.
What happens?
Each gene has a specific role in determining how a person's body is put
together and how it functions. The role of a gene is determined by its
individual DNA code (deoxyribonucleic acid, the chemical coding for a gene).
DNA is made up of four building blocks called bases. These bases are joined
in a specific order for each gene. When a change occurs in the arrangement
of the bases, it can cause the gene not to work properly.
What are genetic disorders?
A structural gene change which can cause a disease or a birth defect is
called a mutation. Genes are inherited in pairs, with one gene inherited
from each parent to make the pair. Cystic fibrosis occurs when both genes
in the pair have a mutation. A person with cystic fibrosis inherits one CF
gene from each parent. Cystic fibrosis is a genetic disorder caused by
inheriting a pair of genes that are mutated or not working properly.
The Cystic Fibrosis Gene
Everyone inherits two copies of the CFTR (cystic fibrosis transmembrane
conductance regulator) gene. However, some of the inherited copies are
mutations. To date, over 700 mutations of the CFTR gene have been
identified. A person with CF inherits two mutated copies of the CFTR gene.
These mutations can either be homozygous, the same, or heterozygous,
different mutations. The most common mutation is delta F508, accounting
for approximately 70% of all mutations. Those homozygous for this mutation
tend to be pancreatic insufficient.
What Does the Mutation Do?
The CFTR gene is a protein that functions as a chloride channel. A
chloride channel helps maintain the proper balance of salt and water within
a cell. A mutation in CFTR causes a dysfunction of the salt and water
balance. This causes dehydration of the secretions (thick mucous) and
excessive loss of salt in sweat.
What is a carrier?
A carrier is a person who only has one copy of the mutated gene. The
parents of a child with CF each carry one CF gene and one normal gene.
They have no symptoms and no disease.
How does CF occur?
When each of the parents contributes a gene to their child, they could pass
on either their CF gene or their non-CF gene. Each pregnancy could result
in one of three outcomes:
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Can I find out if I have a CF gene?
At the present time, carrier testing is available through a DNA test. If a
family member has CF and the gene mutation is known, discovery of the CF
gene in other family members can be made with great accuracy. If the
specific mutation is not known, the test will be done on the 70%-90% of the
CF genes that are most commonly found, but the test won't be 100% accurate.
The screening test for people without a family history of CF will also be
done on the most common gene mutations, and so cannot be said to be 100%
accurate.
CF and the Lungs
What happens in the lungs:
The lungs are like an upside down tree: the trachea is the trunk, the bronchi are the main branches, the bronchioles are smaller branches, and the alveoli are the smallest little twigs and leaves. Normally, tiny hair-like structures known as cilia remove mucus and other substances from the lungs, and bacteria are cleared out. But, because CF produces thick, sticky mucus, the cilia cannot sweep the lungs, and the bacteria remain. This brings about an immunological response from the body's white blood cells: they race to the scene, fight with bacteria, and promptly die… leaving their remains which also contribute to the stickiness of the mucus. Mucus then builds up in the lungs, and lung function starts to drop. It is this residual infection and poor lung functioning that can cause permanent lung damage over time.
What treatment can be done:
The basic daily care program varies to suit individual needs. These are some common pulmonary therapy treatments:
Common Airway Clearance Techniques:
Lung Infections
What Is an Infection?
An infection occurs when pathogenic microorganisms (like bacteria, viruses, or fungi) invade tissues where they don't belong.
What happens in an infection?
Why Do People with CF have to worry about all this?
People with CF have thick mucus which can trap microorganisms in the lungs. Thick mucus is hard to remove, so the microorganisms remain in the lungs, growing and reproducing. Once these organisms are established in the lungs, there are more frequent lung infections. Infection
weakens the body and the immune system. Repeated infections initiate a cycle of inflammation and infection which soon becomes a chronic condition.
What are the consequences of chronic lung inflammations and infection?
CF and the Digestive System
What is the digestive system?
The mouth is the start of the digestive system. Saliva starts the digestive process. Food is chewed, swallowed, passes down the esophagus into the stomach where more digestion occurs.
But, most digestion occurs in the small intestine. It is here that enzymes help break down food so that it can be absorbed into the bloodstream and used for energy. Enzymes are secreted by the pancreas, a small gland located just above the small intestine. The main job of the pancreas is to secrete these enzymes; it also is the place where insulin is made. After enzymes have broken the food down it is absorbed. Any food not broken down passes into the large intestine and is excreted.
What happens in CF?
Mucous plugs can block the pancreas and prevent enzymes from entering the small intestine, which leads to improper digestion of foods. Without these digestive juices, the intestines cannot absorb fats and proteins completely, so nutrients pass out of the body unused. The stools become very large, lighter in color, greasy, and will float on top of the water in the toilet. Unabsorbed fats may also cause excessive intestinal "gas," an abnormally swollen belly, and abdominal pain or discomfort. Weight loss or difficulty maintaining adequate weight can occur. Not all people with CF are pancreatic insufficient.
What can be done?
In general, the same wholesome foods you would give anyone, child or adult, are suitable for the person with CF. The difference will arise in the quantities that are required and the supplements (vitamins and enzymes) needed to ensure sufficient calories. Sometimes there is a need to add salt to replace what is lost in sweat.
Vitamins: Because of the incomplete digestion of fats, fat-soluble vitamins (A, D, E, and K) may be poorly absorbed. Water-soluble supplements are recommended, with the dose varying according to age.
Enzymes: People with CF can take doses of pancreatic enzymes by mouth to help them digest foods better. Pancreatic enzymes help the body absorb nutrients from food, and reduce both the number and bulk of stools, and the amount of flatulence, abdominal pain, and distension.
Minerals: Since large amounts of sodium and chloride are lost in sweat, salt and salty foods are recommended for all ages. Salt tablets, however, aren't usually prescribed.
Oral supplements: Even with enzyme supplements, people with CF absorb food less efficiently. Some may use oral supplements to augment their total caloric intake.