Tay-Sachs disease occurs when the body lacks an enzyme called hexosaminidase A (Hex A), which normally breaks down a fatty substance in nerve cells. Without it, that substance builds up in the brain and spinal cord and gradually destroys nerve cells over time.¹ There are three forms of the disease, depending on how much of the enzyme the body can use. 

The infantile form of Tay-Sachs disease is the most common and most severe. Symptoms usually begin around 6 months of age with muscle weakness and an exaggerated startle response, and the disease progresses quickly from there. Most children with infantile Tay-Sachs disease do not live past age 5.¹ The juvenile form typically begins later, between ages 5 and the teenage years, and progresses more slowly. The late onset form of the disease can appear anytime from the late teens into adulthood and usually does not affect life expectancy.¹

Everyone has two copies of HEXA, the gene associated with Tay-Sachs disease. When both copies of the gene have a mutation, a disease-causing change, the body cannot make enough working hexosaminidase A, which leads to Tay-Sachs disease.¹
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There is no cure for Tay-Sachs disease, so treatment is palliative and focused on managing symptoms.¹ That makes knowing your carrier status before pregnancy one of the most meaningful things you can do for your future family.

Carrier screening has already made a real difference. In specific populations, the number of babies born with Tay-Sachs disease has dropped by more than 90% over the last 50 years, largely because more people learned their carrier status and made informed choices about family planning.² That progress did not come from a treatment breakthrough. It came from people getting screened when they had time to review options, ideally before they were pregnant.

Tay-Sachs disease is inherited in a pattern called autosomal recessive. A carrier has one working copy of the HEXA gene and one nonworking copy. Carriers have no symptoms at all because the one working copy is enough.¹ If both parents are carriers, each pregnancy has a 25% chance (1 in 4) of the child inheriting a nonworking copy of the gene from each parent and being affected by the disease. There is a 50% chance (1in 2) of the child being an unaffected carrier like the parents, and a 25% chance (1 in 2) of the child inheriting two working copies of the gene.¹

About 1 in 27 people of Ashkenazi Jewish descent carry a change in HEXA, the gene linked to Tay-Sachs disease.² In the general population, the carrier rate is closer to 1 in 250.²

Tay-Sachs disease is most closely associated with Jewish ancestry. Specifically, individuals of Ashkenazi Jewish ancestry have the highest known risk. But it isn't the only ancestry group at elevated risk. People of Irish, Cajun, French Canadian, and Pennsylvania Dutch descent also carry a change in the HEXA gene more often than the general population.² Because of this, Tay-Sachs disease testing is recommended for anyone planning a pregnancy or already pregnant, regardless of ethnicity or family history.²

A positive result means you carry one working copy and one nonworking copy of HEXA.¹ You are not affected by Tay-Sachs disease and are not expected to develop symptoms, but you can pass on the nonworking copy to a child. If you're planning a pregnancy,  your partner should also be screened prior to conception, since your child's risk depends on whether your partner carries a change in the same gene.³ The same applies if you are planning a pregnancy using a sperm or egg donor.

A negative result means you have a significantly lower chance of being a carrier for Tay-Sachs disease without bringing it all the way to zero, since no screen can detect every possible gene change.

If both partners carry a change in HEXA, each pregnancy has a 25% chance of being affected by Tay-Sachs disease.¹ If you are already pregnant, prenatal testing for Tay-Sachs disease, such as chorionic villus sampling (CVS) or amniocentesis, can diagnose whether a current pregnancy is affected prior to birth.¹ Genetic counseling is strongly recommended at this stage, and every jscreen result comes with access to a board certified genetic counselor to walk through what your specific results mean and what your options are. We highly recommend testing prior to conception, which allows for the greatest range of reproductive options.