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Screening for Tay-Sachs Disease

by Marjorie Greenfield, M.D.
reviewed and revised by Marjorie Greenfield, M.D.
Tay-Sachs disease is a devastating and untreatable neurological condition that leads to death in early childhood. Around the age of five months, the child starts to lose motor skills and later develops seizures. Death occurs by age of four or five years. Tay-Sachs is passed genetically in a recessive fashion, meaning that if both parents are carriers, approximately one in four of their offspring will have the condition.

Who is at risk?
Tay-Sachs disease is most common in Jews of European descent called Ashkenazi Jews: 1 in 30 carries the trait. People of French Canadian and Cajun ancestry are also at increased risk; all others have about a 1 in 300 chance of carrying the gene.

Who should be tested?
Current guidelines recommend testing couples in which one or both partners may be at increased risk. The risk groups include all people of Eastern European Jewish, French Canadian and Cajun ancestry and those in whom there is a possible family history of Tay-Sachs disease.

Canavan Disease
While less well-known than Tay-Sachs Disease, Canavan Disease is a similar genetic condition that is most common in Jews of Eastern European ancestry. While you are getting Tay-Sachs testing, be sure to ask about other genetic conditions that can be checked out at the same time.

What testing entails
Blood is collected from the person to be checked. Pregnancy and oral contraceptive use interfere with the results of the Tay-Sachs test, leading to false positives, so it's best to do the testing before becoming pregnant. If the woman is already expecting, some experts recommend testing the baby's father first, since if his test is negative, the fetus will not have the disease.

There are some technical ways to modify the test to avoid false positives, including white blood cell (leukocyte) testing and DNA analysis. If the results are ambiguous, a genetics counselor can help to clarify the situation and support the couple in thinking through their options.

What if the tests are positive?
If both parents are found to be carriers, prenatal diagnosis can be offered, using chorionic villi sampling, a test where a small sample of placental tissue is removed either through the cervix or through the abdomen in the later first trimester or amniocentesis, to determine if the fetus is affected.
 RELATED INFORMATION
*  Getting Good Prenatal Care
*  Screening for Cystic Fibrosis in Pregnancy
*  Triple Check or Quad Screen Testing in Pregnancy
*  Genetic Testing in Pregnancy
*  Birth Defects


Created October 12, 2001
Reviewed and revised August 27, 2004
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