Cystic Fibrosis
| Question | Answer |
|---|---|
| What is cystic fibrosis (CF)? | Cystic fibrosis (CF) is a genetic disorder. It is caused by an abnormal gene that is passed from parent to child. It is a lifelong illness that affects all of the organs of the body and often causes problems with digestion and breathing. It does not affect a person's looks or mental ability. In some cases, CF poses a serious risk to a person's health and shortens the life span. Despite their physical tribulations, many people with CF attend school, have careers, and lead full lives. |
| What causes CF? | Cystic fibrosis is a recessive disorder. In a recessive disorder, both parents must carry a copy of the abnormal gene for the problem to occur in their child. A person who has one copy of an abnormal gene for a recessive disorder is a carrier for that disorder, even though he or she may show no signs of it. If both parents are carriers, each of their children has a 25% chance of having the disorder. Put another way, this couple has a 1-in-4 chance of having a child with CF. |
| What are the symptoms of CF? | The symptoms of CF can vary in type and severity. Many people with CF produce a thick, sticky mucus in their bodies. This mucus builds up and clogs the lungs, which makes it hard to breathe, and can lead to infection. It also can affect the digestive organs, making it hard for the body to break down and absorb food. Most males with CF are sterile and cannot father children. |
| Is treatment available for CF? | New drugs and treatments have improved the outlook for people with CF, but it is still a lifelong disease. To treat lung problems, most children with CF need to have physical therapy for about a half hour every day. This therapy helps clear mucus from the lungs. It is easy to do and can be done by parents or other family members. |
| What are risk factors for CF? | The risk of being a CF carrier is higher in certain races and ethnic groups. It occurs more often in white people than in other racial groups. The risk also is increased in families with a history of CF. |
| Can I be tested to assess whether I am a CF carrier? | Carrier testing can be done for couples planning a pregnancy or during pregnancy to assess their risk. The test is done on a blood sample. Carrier testing also is available to all pregnant women. If testing shows that a couple is at high risk, more testing can be done during pregnancy to see whether their fetus has CF. |
| What does it mean if test results for one partner are negative? | If your test results are negative, the chance that you are a CF carrier is small. There are some rare CF gene defects that the test does not detect. For this reason, you could be told your test result is negative, and you could still be a carrier. The likelihood of this is very small. |
| What does it mean if test results for one partner are positive? | If the test results show that one partner is a carrier, the next step is to test the other partner. Both parents must be CF carriers for the baby to have CF. If one parent has a negative test result, the chance that the baby will have CF is small. Because the risk is small, if one partner is a carrier but the other has a negative result, no further testing is recommended. If the father is not available for a carrier test, a genetic counselor may be able to help you decide whether to have prenatal testing of the fetus to see if it has CF. |
| What does it mean if test results for both partners are positive? | If two people who are both CF carriers have a baby, there is a 25% chance that the baby will have CF. However, it is more likely that the baby will be a carrier, like the parents, and will have the gene but will not have the disease. It also is possible that although the parents are both carriers, the baby will not be a CF carrier. |
| If both partners are positive, what follow-up tests are appropriate and what do they assess? | If both partners are CF carriers, further prenatal testing can be done to see if the baby has CF. This testing is not recommended when only one partner is a carrier. Parents may want to know if the baby will have CF so that they can prepare for the care of a child with special health care needs, or they may choose to end the pregnancy. |
| What prenatal tests can be done to detect CF and other disorders? | Prenatal tests done to detect CF and other disorders are chorionic villus sampling (CVS) and amniocentesis. CVS can be performed after 9 completed weeks of pregnancy. Amniocentesis can be performed between 15 weeks and 20 weeks of pregnancy. |
| What are my options if diagnostic test results show that the fetus has CF? |
Two options are available:
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| What should partners who are CF carriers be aware of when thinking about future pregnancies? |
If a test result shows that you are a CF carrier, the result is definite and will not change. If both partners are carriers, it means that in each pregnancy the baby will have a 25% (1-in-4) chance of having CF. If you want to know whether your baby will have CF, you will need to have amniocentesis or CVS in each pregnancy. Other options include the following:
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If your test results are negative, the chance that you are a CF carrier is small. There are some rare CF gene defects that the test does not detect. For this reason, you could be told your test result is negative, and you could still be a carrier. The likelihood of this is very small.
If two people who are both CF carriers have a baby, there is a 25% chance that the baby will have CF. However, it is more likely that the baby will be a carrier, like the parents, and will have the gene but will not have the disease. It also is possible that although the parents are both carriers, the baby will not be a CF carrier.
Two options are available:
- Continue the pregnancy and prepare for a child with CF. Couples can use this time to learn as much as possible about the disease, current treatment options, and the experiences of other families who have a child with CF.
- End the pregnancy. Each state has its own laws on pregnancy termination. You should discuss this decision with your health care provider. You also may want to talk with your partner, counselors, and close friends.
If a test result shows that you are a CF carrier, the result is definite and will not change. If both partners are carriers, it means that in each pregnancy the baby will have a 25% (1-in-4) chance of having CF. If you want to know whether your baby will have CF, you will need to have amniocentesis or CVS in each pregnancy. Other options include the following:
- Adoption
- Using donor sperm or donor eggs (but the donor should be tested for CF carrier status)
- Using in vitro fertilization with your own sperm and eggs, and then using preimplantation genetic diagnosis to see if the fertilized egg has CF or is a CF carrier.
Spinal Muscular Atrophy (SMA)
Spinal muscular atrophy is the most common inherited cause of early childhood death. Normally, healthy nerve cells in the brain called motor neurons send messages to the muscles to tell them when and how to move. But SMA damages these brain cells and prevents those important messages from reaching the muscles. When the muscles don’t get direction on how to move, they become inactive, get smaller, and begin to waste away (a condition known as atrophy). SMA does not affect intelligence. There is no cure or treatment.
There are several types of SMA. The most common form, Type 1, which affects about 70 percent of patients with the disease, is the most severe. Children with Type 1 SMA usually die from respiratory failure before the age of two. Children with type 2 SMA may be able to sit unaided but cannot stand or walk unaided. Although they face many challenges, children with type 3 SMA are able to walk unaided and have a normal lifespan. Type 4 is the adult form of the disorder. Most people affected by this type start having symptoms after age 35, and these symptoms slowly get worse over time. Because it develops slowly, many people with type IV SMA don’t know that they have it until years after symptoms begin.
- The purpose of this test is to determine whether I am a carrier of one of the common genetic abnormalities that cause SMA.
- This test does not detect all carriers of this disease. The decision to have carrier testing is completely mine.
- If I am a carrier, testing my partner will help me learn more about the chance our baby could have SMA.
- If one parent is a carrier and the other is not, it is still possible that the baby will have SMA, but the chance is less than 1 percent.
- If both parents are carriers, prenatal testing is available to find out whether or not the baby has inherited the abnormal SMA genes.
About one in every 40 people carries a mutated SMN1 gene, and every year, about one in every 6,000-10,000 babies is born with SMA.
Please make sure you understand the following points. If you are unclear, ask your healthcare provider before deciding on this test.
Fragile X Syndrome
Fragile X is caused by a change in the Fragile X Mental Retardation gene. This abnormal gene can be passed from generation to generation. Fragile X syndrome is usually passed on by a gene that is carried by a woman. One in 259 women are carriers. Fragile X is found in all ethnic groups and can occur in families with no history of mental retardation or autism.
Fragile X Syndrome is the most common inherited cause of mental impairment. Fragile X affects approximately 1 in 4,000 males and 1 in 8,000 females. The majority of males with Fragile X have significant intellectual disability. The spectrum ranges from learning disabilities to severe mental retardation and autism. About one third of the females affected with Fragile X have significant intellectual disabilities.
- The purpose of this test is to determine whether I am a carrier of one of the common gene abnormalities that cause Fragile X Syndrome.
- This test does not detect all carriers of this disease.
- The decision to have carrier testing is completely mine.
- If I am a carrier, prenatal testing is available to find out whether or not the baby has inherited the abnormal fragile X gene.
If a mother is a carrier, there is a 50 percent chance to have a child with Fragile X Syndrome.
Please make sure you understand the following points. If you are unclear, ask your healthcare provider before deciding on this test.
Glossary
| Word/Term | Definition |
|---|---|
| Amniocentesis | A procedure in which a needle is used to withdraw and test a small amount of amniotic fluid and cells from the sac surrounding the fetus. |
| Carrier | A person who shows no signs of a particular disorder but could pass the gene on to his or her children. |
| Chorionic Villus Sampling (CVS): | A procedure in which a small sample of cells is taken from the placenta and tested. |
| Fetus | The developing offspring in the uterus from the ninth week of pregnancy until the end of pregnancy. |
| Gene | A DNA "blueprint" that codes for specific traits, such as hair and eye color. |
| Recessive Disorder | A type of a genetic disorder in which one copy of the defective gene must be passed from each parent for a child to be affected. |
| Preimplantation Genetic Diagnosis | A type of genetic testing that can be done during in vitro fertilization. |