The American College of Obstetrics and Gynecology (ACOG) recommends genetic carrier screening, testing to determine the risk of having a child with a genetic condition, for couples planning a pregnancy. Many fertility clinics now use an expanded carrier screening panel that includes testing for Tay-Sachs disease as part of their strategy for all couples regardless of ancestry. Because of this expanded carrier screening, more couples are being identified as carriers who are good candidates for PGT for Tay-Sachs disease.
What Is Tay-Sachs Disease?
Tay-Sachs disease is a fatal genetic disorder caused by an autosomal recessive gene. It progressively destroys neurons — or nerve cells — in the brain and spinal cord, according to NIH’s Genetics Home Reference. The symptoms of Tay-Sachs are due to the lack of a critical enzyme called beta-hexosaminidase A, says the NIH. Beta-hexosaminidase A prevents the accumulation of a fatty substance called GM2 ganglioside in nerve cells of the brain. Without this enzyme, GM2 ganglioside builds up and causes damage to cells.
Most babies born with the most common form of Tay-Sachs disease appear normal until about three to six months of age when typical development begins to slow, and infants may lose motor skills. By toddlerhood, most children will experience regression, recurrent seizures and diminishing cognitive function. The majority of children with Tay-Sachs disease will not live past the age five — there is no cure, and treatment is aimed at managing the symptoms.
Although Tay-Sachs disease is commonly thought to affect mostly Jewish families, it most often affects families with no known history of the disease, regardless of ancestry. Today, the vast majority of babies born with Tay-Sachs are not Jewish. Due to awareness in Jewish populations, there are fewer Jewish babies being born with Tay-Sachs. While expanded carrier screening has identified an increasing number of non-Jewish individuals as carriers, it is not offered by all fertility clinics and OB/Gyn providers.
Carrier screening for Tay-Sachs can be performed by DNA (genetic) testing as well as by an enzyme screening, which looks at the level of protein produced by the gene that produces beta-hexosaminidase A. There are many mutations in this one gene that can cause Tay-Sachs, and the National Tay-Sachs & Allied Diseases Association recommends a combination of genetic and enzyme testing for the most sensitive results.
We Both Carry Tay-Sachs Mutations: What Are Our Options?
If you and your partner both carry mutations in the Tay-Sachs gene, you may choose to pursue in vitro fertilization (IVF) with preimplanation genetic testing (PGT),which will test the embryos before being transferred to the uterus. You can choose to implant only those embryos that are unaffected by the mutation.
Chorionic villi sampling (CVS) and amniocentesis are also options to discuss with your physician or a genetic counselor; however, these prenatal diagnostic tests can only detect Tay-Sachs disease in an existing pregnancy.
How Does PGT Work for Couples Who Carry the Tay-Sachs Mutation?
PGT for Tay-Sachs disease follows the same process as PGT for other single gene disorders. A custom test is built for your embryos using DNA from family members, and the embryos are tested for the mutations you or your partner carry. To confirm that the fetus does not have Tay-Sachs, it is recommended to have additional prenatal testing, such as CVS or amniocentesis, or test after birth.
Holly and Todd McDonald chose to do PGT after their first child, Cora, was diagnosed with Tay-Sachs disease. McDonald says she wishes they’d had carrier testing done before having Cora, who was conceived with IVF, but their clinic did not recommend it for families without Jewish ancestry.
The McDonalds wanted more children, but they were not willing to put another child or their family through Tay-Sachs. “Everybody gets to choose how they build their family,” says McDonald. “But if you don’t know what you carry, then you don’t get to choose — you don’t have the choice to do something different.”
McDonald gave birth to her second child — a daughter who does not have Tay-Sachs — when Cora was almost three years old. She is now pregnant with a son from the same IVF cycle, who tested negative for Tay-Sachs as well. To confirm the results, they chose not to pursue prenatal testing via CVS or amniocentesis, but had their daughter tested again after birth via a blood test. They plan the same for their third child.
“I feel a ton of relief that my second daughter doesn’t have Tay-Sachs,” says McDonald. “[PGT] was the right choice for us to build our family.”
For more information about the McDonalds’ story, please visit their Facebook page, Celebrating Cora.
September is Tay-Sachs Disease Awareness Month! For more information on Tay-Sachs disease, please visit the National Tay-Sachs & Allied Disease Association (NTSAD), Jewish Genetic Disease Consortium (JGDC) and Cure & Action for Tay-Sachs Foundation (CATS).