Hemoglobin Disorders:
Thalassemia Disease more common in:
Asian, Southeast Asian, Mediterranean people
Sickle Cell Diseases more common in:
Black/African-American people
Cystic Fibrosis more common in:
Caucasians/Whites (non-Hispanic) people
Tay-Sachs Disease more common in:
Jews (Ashkenazi/Eastern European) people
Canavan Disease more common in:
Jews (Ashkenazi/Eastern European) people
Familial Dysautonomia more common in:
Jews (Ashkenazi/Eastern European) people
All of our genes come in pairs; we get one from each parent. In order to have one of the above diseases, a baby must receive two non-working genes for the same disease, one from each parent. A person who has only one non-working gene for one of these diseases is called a carrier. Being a carrier for one of the above-mentioned conditions does not affect a person's health in any way.
Who carries genetic diseases?
Every person has some genes that do not work properly, so everyone is a carrier for some genetic diseases. However, certain genetic diseases such as those above, occur more often in specific ethnic and racial groups than in the general population. You do not need to have a family member with one of these diseases to be a carrier. Usually there is no family history, so most people do not know whether they are carriers.
What does it mean to be a carrier?
Being a carrier does not cause any health problems. However, if both parents are carriers for the same genetic disease, there is a chance that their child will have the disease. Please see our section on inheritance patterns in Genetics 101. A child will have one of these diseases only if he or she inherits the same non-working gene from each carrier parent. This inheritance pattern is known as “autosomal recessive" inheritance.
When both parents are carriers for the same genetic disease, there is a 1 in 4 (or 25%) chance that the baby will have the disease. There is also a 3 out of 4 (or 75%) chance that the baby will not have the disease.
If only one parent passes on a non-working gene to a baby, the baby will not have a disease, but will be a healthy carrier just like the parent.
For more information about being a carrier for certain genetic conditions, please click on the links below:
What does it mean to be a carrier for cystic fibrosis?
What does it mean to be a carrier for Tay-Sachs disease?
What does it mean to be a carrier for Canavan disease?
What does it mean to be a carrier for familial dysautonomia?
What does it mean to be a carrier for thalassemia (alpha or beta)?
What does it mean to be a carrier for sickle cell disease (or other hemoglobinopathy)?
How can I know if I am a carrier?
Ethnicity-based screening is part of the initial prenatal work-up for all prenatal patients in Northern California Kaiser Permanente. If a woman is identified as a carrier, screening is then offered to the father of the baby.
You will be offered carrier testing for certain conditions if you or your baby’s father has an ethnic background that is associated with a higher chance of being a carrier. The following are the ethnicity criteria for testing:
If you have any Southeast Asian background you may be tested to learn if you are a carrier for hemoglobin E or another hemoglobin disease.
If you OR your baby’s father have any Black/African American background you may be tested to learn if you are a carrier for sickle cell disease or another other hemoglobin disease.
If you OR your baby’s father have any Caucasian/White background you can have testing to learn if you are a carrier for cystic fibrosis.
If you AND your baby’s father have any Ashkenazi Jewish (Eastern European Jewish) background you can have testing to learn if you are a carrier for Tay-Sachs disease, Canavan disease, and familial dysautonomia.
Table of Screening Tests
Screening begins with the pregnant woman (usually at the same time as her initial prenatal lab work).
Knowing your and your partner’s ethnic background, as well as your family history of genetic conditions, can help determine which screening test would be most useful to you. If you have a family history of any of the mentioned conditions, contact your local Genetics Department to ensure you are getting appropriate testing.
What does a negative result mean?
A negative result means that you are most likely not a carrier for that particular disease. Therefore, no further testing is generally needed.
These tests are very accurate, but they will not identify all carriers.
What does a positive result mean?
A positive result means that you are a carrier for that particular disease. A genetic counselor will tell you of your positive test result, and the father of the baby will be offered testing. If his test is negative, this is reassuring, because there is only a very small chance that your baby will have the disease for which you are a carrier, and no more testing will be done.
If the father of the baby is also found to be a carrier of the same condition, this means that there is a 25% chance for the baby to have the disease. If this happens, a genetic counselor will meet with you to discuss the option of testing the baby before it is born. This is called Prenatal Diagnosis. Prenatal diagnosis can determine whether the baby is affected before it is born.
There are no prenatal treatments to help lessen the symptoms of these conditions, and the disorders are not curable. Some people who learn that their baby will have one of these diseases may choose not to continue their pregnancy. Others may use this information to help them prepare for taking care of a child with special medical needs. Your genetic counselor can help you make these decisions and give you ongoing support.
If you choose to not have prenatal testing, the baby can be tested shortly after it is born. The California Newborn Screening Program tests for cystic fibrosis, sickle cell disease, and the thalassemia diseases, along with certain other metabolic and endocrine disorders.
Preconception screening
Women who are planning a pregnancy, can also be offered preconception ethnicity-based screening (i.e., screening before the pregnancy begins). The same guidelines followed by the prenatal screening program should be followed for preconception screening. Preconception screening has the advantage of giving couples at high risk additional options for conceiving a pregnancy unaffected by the condition. Any woman interested in preconception screening can arrange testing through her obstetrician.
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