Children's Health

What is Tay-Sachs disease?

Tay-Sachs is a rare disease that is passed down through some families. A person with Tay-Sachs has changed (mutated) genes that don't make any or enough of an enzyme called hexosaminidase A (hex A). Hex A breaks down fatty compounds. Without it, fatty compounds build up in the brain and nerve cells and cause damage.

There are two forms of Tay-Sachs:

• The most common form develops soon after a baby is born. It causes death early in childhood.
• Late-onset Tay-Sachs can start between puberty and the mid-30s. How long a person lives depends on how severe the symptoms are. People may live as long as someone who doesn't have Tay-Sachs disease.

What causes Tay-Sachs disease?

Tay-Sachs can occur when parents pass on a changed gene to their child.

• If a baby gets the gene from both parents, he or she will get the disease.
• If the baby gets the gene from only one parent, he or she will be a carrier. This means that the child will have one gene that produces hex A and one that doesn't. The child's body makes enough hex A so that he or she doesn't get the disease. But the child can pass the gene on to his or her children.

In late-onset Tay-Sachs (LOTS), the body makes a small amount of hex A. People with LOTS inherit the late-onset hex A gene from both parents or inherit one late-onset gene and one inactive gene.

The Tay-Sachs gene is most common in people of Ashkenazi Jewish descent. About 1 out of 30 people in this population is a carrier of the disease.¹ People of French-Canadian descent from the East Saint Lawrence River Valley of Quebec and people of Cajun descent in Louisiana are also more likely to carry the gene than others.

What are the symptoms?

A child with Tay-Sachs disease looks healthy at birth. But when your child is:

• 3 to 6 months of age, you may notice that your child makes less eye contact and has a hard time focusing his or her eyes on things. A doctor may see a red spot on your child's retina.
• 6 to 10 months of age, you may notice that your child is not as alert and playful as he or she had been. It might be hard for your child to sit up or roll over. You also may notice that your child does not see or hear well.
• 10 months and older, the disease gets worse quickly. Your child may have seizures, have an intellectual disability, lose his or her vision, and not be able to move.

Children with Tay-Sachs rarely live beyond 4 or 5 years of age.