What Are Ashkenazi Jewish Genetic Diseases?
Ashkenazi Jewish genetic diseases are a group of rare disorders that occur more often in people of Eastern European (Ashkenazi) Jewish heritage than in the general population. Even though most of these diseases are severe and life-limiting, some can be treated to reduce symptoms and prolong life. Some of these diseases can be found during pregnancy through chorionic villus sampling (CVS) or amniocentesis. This testing is done usually if one or both parents are carriers of a genetic disease.
Diseases in this group include:
- Bloom syndrome. Babies with this disease are born small and remain shorter than normal as they grow. Their skin may look red, and they have more lung and ear infections than children normally have.
- Canavan disease. This disease gradually destroys brain tissue.
- Cystic fibrosis. This disease causes very thick mucus in the lungs and problems with digesting food.
- Familial dysautonomia (FD). People with this problem cannot feel pain, they sweat a lot, and they have trouble with speech and coordination.
- Fanconi anemia. People with this problem do not have enough blood cells and have problems with the heart, kidneys, arms, or legs. They also are more likely to get cancer.
- Gaucher disease. This disease causes a type of fat called glucocerebroside to build up in certain cells of the liver, spleen, and bone marrow.
- Mucolipidosis IV. This problem causes the nervous system to deteriorate, or break down, over time.
- Niemann-Pick disease (type A). This disease causes a type of fat called sphingomyelin to build up in cells of the liver, spleen, lymph nodes, and bone marrow.
- Tay-Sachs disease. This disease causes a type of fat called ganglioside to build up in the cells of the brain and nervous system.
- Torsion dystonia. People with this problem have ongoing spasms that twist the muscles in their arms, legs, and sometimes their body. Testing for this condition may not always be done.
About 1 out of 4 people of Ashkenazi Jewish heritage is a carrier of one of these genetic conditions, most commonly of Gaucher disease, cystic fibrosis, Tay-Sachs disease, familial dysautonomia, or Canavan disease.footnote 1
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What Is an Ashkenazi Jewish Genetic Panel (AJGP)?
An Ashkenazi Jewish genetic panel (AJGP) is a blood test that looks for genetic diseases that occur more often in people of Eastern European (Ashkenazi) Jewish heritage. These diseases do not just affect people of Ashkenazi Jewish heritage but are more common in this group of people. Other racial and ethnic groups have genetic diseases that are more common in their groups.
An AJGP test tells parents if they have an increased chance of having a child with certain genetic diseases. Anyone who is interested in knowing his or her carrier status can ask for the test, but a doctor must order the test. Different labs may have different tests in the panel.
Talk to your doctor about which diseases are important for your family. Genetic counselling can help you understand the test and possible results so you can make the best decision for you.
What Is Carrier Screening?
A carrier is a person who can pass a genetic disease on to his or her children but does not have the disease. Carrier identification is a type of genetic test that can help show whether people of high-risk groups (certain ethnic groups or a family history of a disease) for a specific disease are likely to pass that disease to their children. This type of test can guide a couple's decision about having children and making choices about diagnostic tests during a pregnancy.
An Ashkenazi Jewish genetic panel (AJGP), done on a blood sample, can see whether you or your partner is a carrier of gene changes that cause certain genetic diseases. If positive, the test can help show whether you and your partner have an increased chance of having a child born with one of these diseases.
Who Should Be Tested?
Genetic tests can be done for anyone who wants to know whether he or she is a carrier of certain diseases. The Ashkenazi Jewish genetic panel (AJGP) shows the chance of having a child with a disease that is more common among people of Eastern European Jewish heritage. Anyone who is interested in knowing his or her carrier status can ask for the test, but a doctor must order it.
Genetic test results often raise ethical, religious, or legal concerns. You should have genetic counselling before making a decision about testing. Genetic counsellors are trained to explain the test and its possible results clearly. A genetic counsellor can help you make well-informed decisions.
An AJGP may be recommended for people of Eastern European Jewish heritage, including:
- Partners of people with diseases on the test panel.
- Couples planning to have children.
- Pregnant women (and their partners) who seek prenatal care, whether they have a history of genetic diseases or not.
- Adults with a positive family history of a disease that is on the test panel.
If only one member of a couple has Ashkenazi Jewish heritage, testing will be offered for Tay-Sachs disease only. If test results show that the person is a carrier of Tay-Sachs disease, then his or her partner also may be tested.
What If I Am a Carrier?
It is more common to be a carrier of a genetic disease, such as cystic fibrosis (CF), than to have the disease. If tests show that you are a carrier of a disease, your partner also should be tested. Both parents must be carriers of a disease for a child to have the disease.
The tests are not 100% accurate, so a person may test negative and yet be a carrier. If you are a carrier and your partner tests negative, there is still a very small chance that you will have a child with the disease.footnote 1
If you and your partner are both carriers of a genetic disease, there is a 1-in-4 (25%) chance that your child will have the disease.
- If you are not already pregnant, you may wish to have genetic counselling to understand your risks and options if you decide to have children.
- If you are already pregnant, you may wish to have tests, such as amniocentesis or chorionic villus sampling, to help find out whether your baby has a disease.
Is the Test Accurate?
About 90% of the time, the test accurately shows whether or not a person is a carrier of an Ashkenazi Jewish genetic disease. So there is a small chance that you may be a carrier of one of these diseases even if the test results are negative.footnote 1
Should I Be Tested?
The decision to be tested is a personal one. You may wish to be tested if you are concerned that you or your partner might be a carrier of a disease that is on the test panel. Being a carrier is more likely if you have a family member with the disease.
Some people decide to be tested to know their chances for having a child with a disease or for passing an abnormal gene to their child.
Carrier tests are expensive. Another factor that may guide the decision to have the tests is whether the cost of the tests is covered by your health plan.
You may decide to have carrier tests if you are already pregnant and the test results will affect your decision to continue your pregnancy or help you make decisions about caring for your baby.
If you find out you are a carrier of one of these genetic disorders, other members of your family (such as your brothers and sisters) may want to get tested, too.
Why Not Be Tested?
There may be reasons you would choose not to have the carrier tests.
- You are already pregnant and the results will not affect your decision to continue your pregnancy.
- Carrier tests are expensive. You may decide not to have the tests if your provincial health plan or private health insurance does not pay for it.
- The tests are not 100% accurate. There is a small chance that you are a carrier even if the results are normal (false-negative).
Current as of: December 9, 2019
Author: Healthwise Staff
Medical Review: Patrice Burgess, MD, FAAFP - Family Medicine
Brian O'Brien, MD, FRCPC - Internal Medicine
Martin J. Gabica, MD - Family Medicine
Adam Husney, MD - Family Medicine
Siobhan M. Dolan, MD, MPH - Reproductive Genetics
Current as of: December 9, 2019