The term Ashkenazi refers to individuals descended from the medieval Jewish communities of the Rhineland in the west of Germany. Many Ashkenazi Jews (AJ) migrated to other parts of Europe, with the majority migrating eastward. Show
The conditions for which carrier screening is offered are more common in individuals of Ashkenazi Jewish descent than other ethnic groups because of specific mutations that occurred in "founders" of the population. Because Jewish individuals historically married within their own ethnic group, these mutations increased in frequency over generations. What are the Ashkenazi Jewish genetic disorders? Screening is available for eleven genetic disorders. Carrier frequency is different for each condition — the overall chance of being a carrier for at least one of these diseases is 1 in 4 to 1 in 5 for someone of AJ descent. Of these conditions, Canavan disease and Tay-Sachs disease are among the most common and severe. Both are progressive conditions with no effective treatment options at this time. Canavan disease and Tay Sachs disease are usually fatal in childhood. Cystic fibrosis (CF) is also common in individuals of Caucasian ancestry. All of these disorders are also found in non-Jewish individuals, but with lower incidence (with the exception of CF). Clinically Available Screening for Individuals of Ashkenazi Jewish Descent*
* Disease incidence, carrier frequency and detection rates among individuals who are not of Ashkenazi Jewish descent are available by contacting a genetic counselor at the UCSF Prenatal Diagnostic Center. Who should consider carrier screening? Based on recommendations from the American College of Medical Genetics, the American College of Obstetrics and Gynecology, and other groups, you should consider carrier screening if you, your partner, or both are of AJ descent. Carrier screening is typically performed stepwise by screening the individual with AJ ancestry. It is recommended to start with testing of the Ashkenazi Jewish partner and to test the non-Jewish member of the couple only if the Jewish partner is a carrier of any of the diseases. Carrier screening is less sensitive and less informative in non-Jewish individuals. When both partners are AJ, carrier screening can be done on either partner. Carrier screening can be done simultaneously for both parents, if time is a constraint. When should testing be done? The ideal time to undergo carrier screening is before pregnancy, but carrier screening can be done during pregnancy. If you are already pregnant, we recommend having carrier screening as early in the pregnancy as possible so the results are available to you for further decision making. What will the results tell me? All of these conditions are inherited in an autosomal recessive manner. Your test could reveal several different results:
How do I arrange screening? If you are interested in pursuing carrier screening for some or all of these conditions, please contact the Prenatal Diagnostic Center for an appointment. Please note that medical insurance plans vary widely. Plans may cover the cost of screening at different rates. Our office can help you determine your plan's coverage and facilitate an insurance authorization if required.
Tay-Sachs disease is a genetic condition. Tay-Sachs is caused by a baby receiving two defective HEXA genes, one from each parent. Tay-Sachs disease symptoms include failing to meet motor milestones, such as sitting and standing. Babies born with Tay-Sachs often die at a young age. Genetic testing can help you make family planning decisions.
Tay-Sachs disease affects the nerve cells in the brain and spinal cord. Babies with Tay-Sachs lack a particular enzyme, which is a protein that triggers chemical reactions in cells. The lack of the enzyme, hexosaminidase A, causes a fatty substance to collect. The buildup of this substance, GM2 ganglioside, leads to Tay-Sachs symptoms such as muscle weakness. Tay-Sachs is a genetic condition. It’s caused by changes in a pair of genes inherited from parents. It’s a progressive disease, meaning it gets worse over time. Children born with Tay-Sachs often die by age 4, usually from complications of pneumonia. There’s no cure, with treatment aimed at supporting the child and keeping them comfortable. Genetic testing is available for couples who may face a higher risk for having a baby with Tay-Sachs. Genetic testing and counseling can help parents-to-be make informed decisions about family planning. Who is at risk for Tay-Sachs?People across racial and ethnic groups can carry a genetic change tied to Tay-Sachs disease. But it’s much more common among people of Ashkenazi (Eastern European) Jewish descent. Other populations with higher numbers of people carrying the disease-causing genetic change include:
How common is Tay-Sachs disease?For people not from high-risk backgrounds, around 1 in 300 people carry the genetic change (or variant gene) for Tay-Sachs. For people of Ashkenazi Jewish descent:
What are the forms of Tay-Sachs?There are several forms of Tay-Sachs disease. The type a child has depends on when symptoms develop. Families usually only have one form of the disease. So if a child has infantile Tay-Sachs, it’s not likely that older siblings will develop juvenile or late-onset Tay-Sachs:
Are there similar diseases?The symptoms and progression of Tay Sachs are like those of Sandhoff disease, another inherited condition. Sandhoff disease involves hexosaminidase A and a second enzyme, hexosaminidase B.
Tay-Sachs comes from a disease-causing variant (change) to the HEXA gene. Each baby has two copies of the HEXA gene, one from their biological father and one from their biological mother. Tay-Sachs happens when both parents had a variant HEXA gene and passed it on. That means neither copy of the baby’s HEXA gene works well. Healthcare providers call this hexosaminidase A deficiency, or hex A deficiency. What does it mean to be a Tay-Sachs carrier?A carrier has one working copy of the HEXA gene and one copy with a disease-causing variant. Carriers don’t have the disease or show symptoms, since their bodies can rely on the working gene. But if two carriers have children together, there’s a:
What are typical symptoms of Tay-Sachs disease?Symptoms of the most common form of Tay-Sachs start developing when babies are around 3 to 6 months old. The symptoms continue to progress as the child gets older. Children often don’t meet their developmental milestones. Symptoms at 3 to 6 months:
Symptoms at 6 to 10 months:
Symptoms at 8 to 10 months:
At around a year and a half (18 months), the child’s head size starts to grow. When they’re 2 years old, they often have trouble swallowing. They may end up in an unresponsive state. This means they don’t have much brain function. Age of death is usually between 2 and 4 years old. Pneumonia is often the cause of death. How do other forms of Tay-Sachs progress?Less often, someone may have another form of Tay-Sachs, also caused by a hexosaminidase A deficiency. These other forms progress differently and may include additional symptoms: Juvenile hexosaminidase A deficiency:
Chronic hexosaminidase A deficiency:
Late-onset hexosaminidase A deficiency:
To diagnose Tay-Sachs disease, healthcare providers do a blood test. They measure the level of hexosaminidase A in the body. In a child with classic Tay-Sachs, this protein is mostly or completely missing. People with other forms of the disease have reduced levels. A provider may also do an eye exam to see if the child has the classic cherry-red spot in the eye. How can genetic counseling help families at risk for Tay-Sachs disease?Genetic counseling is available for:
How genetic counseling works:
You can also talk to your provider about:
When should I do genetic testing for Tay-Sachs?The best time to do genetic counseling and testing is before pregnancy. That way, you’ll have all the information you need to make the best decisions for you and your family.
There’s no cure for Tay-Sachs disease. Treatment options aim to control some of the symptoms. For example, your provider may prescribe medication to control seizures. Other treatment measures include providing proper nutrition and hydration. Children are also made as comfortable as possible. Researchers continue to explore more care options.
There’s no way to prevent Tay-Sachs disease. It’s an inherited condition. Children get it from receiving two variant genes from their parents. The best way to prevent Tay-Sachs is to have genetic testing before getting pregnant. Preconception counseling with your healthcare provider can help you plan for a future pregnancy.
Most forms of Tay-Sachs disease are fatal. Children with Tay-Sachs often pass away by age 5. Your child’s care team will talk to you about end-of-life issues. They’ll walk you through decisions about how and where you’d like your child to receive care. They’ll also discuss what you’d prefer to do if your child’s lungs stop working.
The best way to care for your child is to manage their symptoms and keep them comfortable. Your care team will work with you on:
When should I see my healthcare provider?Talk to your provider if:
What else should I ask my healthcare provider?If you’re at high risk for having a baby with Tay-Sachs, ask your provider:
A note from Cleveland Clinic Tay-Sachs disease is a rare genetic condition. It happens when each biological parent passes down a variant HEXA gene to a child. It’s more common among people from certain backgrounds, such as Ashkenazi Jewish people. Tay-Sachs disease symptoms include muscle weakness. Children also miss motor milestones, such as not pulling up to standing. There’s no cure for Tay-Sachs disease. Treatment seeks to improve quality of life and keep children comfortable. Most children born with Tay-Sachs pass away before their fifth birthday. Genetic testing can help you find out if you or your partner is a Tay-Sachs carrier. You can then make informed decisions about family planning. If you’re planning a pregnancy and at high risk for Tay-Sachs, talk to your healthcare provider.
Last reviewed by a Cleveland Clinic medical professional on 12/18/2020. References
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