What Is CF?
Cystic fibrosis (CF) is a life-threatening genetic disease passed from parents to children. It causes mucus to build up and clog some of the organs in the body, particularly the lungs. When mucus clogs the lungs, it can make breathing very difficult. The thick mucus also causes bacteria (germs) to stick in the airways, causing infections that lead to lung damage.
Mucus also can block the digestive tract and pancreas. The mucus stops digestive enzymes from reaching the intestines. These enzymes are critical because they break down food allowing important nutrients to enter the bloodstream and nourish all organs, such as muscles, bones, and the brain. It is these nutrients that, essentially, help people grow and remain healthy.
Approximately 30,000 children and adults in the USA have CF. An additional ten million more— about one in every 31 Americans— do not have the disease but are carriers of the defective CF gene. CF is most common in Caucasians, but it can affect all races.
Can anyone be a carrier?
Yes. The risk of being a CF carrier is greater in whites than in any other ethnic group. The risk also increases if there is a family history of CF.
If you do not have any family history of CF, your risk will be determined by your ethnic background. CF is common among Caucasian and people of Ashkenazi Jewish descent. CF is less common in Hispanics, African-Americans, Native Americans and Asian people.
A positive CF carrier screening test means you are a carrier of CF. A negative test means you are not a carrier. There are, however rare variations (mutations) that are not included in carrier screening.
Symptoms of CF?
The severity of the symptoms depends on the patient and the genetic mutation. The most common symptoms include the following:
• Salty-tasting skin
• Cough with a lot of mucus production
• Frequent lung infections
• Difficulty breathing and wheezing
• Poor growth/weight gain
• Constipation or greasy and bulky stools
• Nasal polyps
• Male sterility
Chances of having a baby with CF
A carrier is a person who has no signs of disease but can pass the defective gene on to his/her child. CF is a recessive disease, i.e, to have the disease, a person needs two copies of the defective gene.
The following guidelines are related to the inheritance diagram shown. If both parents are carriers, then there is a:
• 25% chance (1-in-4) that the baby will have CF.
• 75% chance (3-in-4) that the baby will not have CF
• 50% chance (1-in-2) that the baby will be carrier
• 25% chance that the baby will not have the disease or be a carrier, which means the baby will have two normal copies of the gene.
It is recommended that all expecting couples or couples planning to have a baby have the CF carrier screening test. The CF carrier screening test must be offered to all pregnant women of all ethnic groups.
If you and your partner have undergone CF carrier screening testing, these results will not change with subsequent pregnancies, and there is no need to repeat the testing. If both parents are carriers, they have the same 25 percent chance with each pregnancy of having a baby with CF. They may opt to have prenatal testing with each pregnancy to determine if the baby is affected.
• CF carrier testing will determine if you and your partner carry an abnormal CF gene. During pregnancy, it is helpful to test both parents. If both parents are carriers, further prenatal testing can be done to determine if the baby has CF.
• If one partner is a carrier, the next step is to test the partner. If the partner is negative, the chance that their baby will have CF is minimal. In this situation, no further testing is recommended.
• Prenatal follow-up tests become necessary if both parents are carriers, and they want to know if the baby is affected. At this point, genetic counseling is recommended before couples make any further decisions. The available tests are amniocentesis, chorionic villus sampling, and preimplantation genetic diagnosis. These test results are very accurate; however, if positive, they will not tell you the severity of the symptoms.
• For newborn testing, diagnosing CF involves a sweat test and a genetic test to look for mutations. The sweat test should be performed only at an accredited clinic, with the expertise to perform this test. The genetic test can be performed from a blood sample or a buccal swab. The sample must be sent to a pathology laboratory that is well-versed in genetic testing.
This information is intended for patient education and information only. It does not constitute advice, nor should it be taken to suggest or replace professional medical care from your physician.
For more information:
Cystic Fibrosis Foundation
6931 Arlington Road
Bethesda, MD 20814
1-800-FIGHT CF 1.800.344.4823
National Society of Genetic Counselors
401 N. Michigan Avenue
Chicago, IL 60611
4301 Connecticut Avenue NW, Suite 404
Washington, DC 20008-2369