Tay-Sachs disease (TSD) is a hereditary disease that leads to death before age five. DNA carrier testing for Tay-Sachs is something that should be done if there is a history of TSD in the family. The disease is characterized by the absence of the enzyme hexosaminidase-A or Hex-A. Without this, the cells in the body begin to accumulate a fatty substance called GM2 ganglioside, especially in the brain. Over time, this progression damages the cells. Babies with Tay-Sachs disease eventually begin to have seizures, experience difficulty moving and blindness. There is currently no cure.
Testing can determine if the parents are carriers and also if the fetus has the condition. The condition is most common in people of Eastern European descent. It’s possible to be a carrier and not know it. 1 in 27 American Jews are carriers of the gene, and if both parents are carriers, the child or children have a 25 percent chance of contracting the disease and 50 percent chance of becoming a carrier, which they can pass on to their own children.
It’s best to sit down with a genetic counselor before undergoing testing to get an accurate history and know which tests to conduct to find out as much information as possible. The counselor might recommend a test to measure both Hex-A and Hex-B levels in your blood to determine if you’re a carrier. A negative result to the test means that you aren’t a carrier, while a positive means that you are a carrier for the disease. When testing a fetus, a negative means that they do not have the gene, while a positive indicates that they do have Tay-Sachs disease.
The test typically consists of taking blood from a vein for the mother or father and an amniocentesis for the mother, which consists of removing a sample of amniotic fluid to test for the mutation with a needle. An alternative method is through choionic villi sampling or CVS, which involves removing a small part of the placenta for testing. An amniocentesis can be performed around the 16th week of pregnancy, while a CVS can be conducted around 11 weeks.
The risks for getting the test done are minor and involve bruising or soreness where the blood was taken. An amniocentesis is generally safe, but can cause fluid leakage, cramping or bleeding and poses a slight risk of fetal injury or miscarriage. It’s up to you and your doctor to determine which tests are most appropriate for your situation and the risks associated with each of them.
If you or your spouse fall into any risk categories you should discuss DNA carrier testing for Tay-Sachs disease with your doctor. This will give you more information about your carrier status and help you make the best reproductive choices for your circumstances.