Conditions Basics

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 nerve cells of the brain 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. Late-onset Tay-Sachs is very rare.

What causes it?

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

• If a baby gets the changed gene from both parents, he or she will get the disease.
• If the baby gets the changed 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 changed 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 change from one or both parents.

The changed gene that causes Tay-Sachs disease is more commonly found in people of Ashkenazi Jewish descent. About 1 out of 30 people in this population is a carrier of the disease. People who have family from the Quebec Bas-St-Laurent or Gaspésie regions or New Brunswick territories, or have a family history of the disease are also more likely to carry the changed gene.^{footnote 1}

What are the symptoms?

A child with Tay-Sachs disease looks healthy at birth. But symptoms increase over time.

3 to 6 months of age.

You may notice that the 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 the child's retina.

6 to 10 months of age.

You may notice that the child is not as alert and playful as he or she had been. It might be hard for the child to sit up or roll over. You also may notice that the child does not see or hear well.

10 months and older.

The disease gets worse quickly. The 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 years of age.

In late-onset Tay-Sachs (LOTS), early symptoms such as clumsiness or mood changes may be minor or seem "normal" and go unnoticed. Later symptoms may include muscle weakness and twitching, slurred speech, and trouble thinking and reasoning. The symptoms depend on how much hex A the body makes.

How is it diagnosed?

If you or your doctor thinks that your child has Tay-Sachs disease, your doctor will do a physical examination and a blood test to check the level of hex A. A genetic test may be needed to be sure the disease is Tay-Sachs.

How is Tay-Sachs disease treated?

The focus of treatment for Tay-Sachs disease is to control symptoms and make your child as comfortable as possible. There is no cure. It may be helpful to seek counselling or find support from others who are going through the same thing you are.

If you have late-onset Tay-Sachs disease (LOTS), treatment also focuses on controlling symptoms. The treatment you receive, such as medicine for depression, depends on the symptoms you have.

It may be overwhelming to learn that your child has Tay-Sachs. It's important that you care for yourself as well as your child. Talk to your doctor about:

• Your concerns and the help you'll need for your child.
• A support group in your area.
• Family counselling to help each member cope with the disease.

As the disease gets worse, your child will need more care. Encourage your child to be as active as possible for as long as possible. Give your child your love and affection.

You may not be able to care for your child without help. Talk with your doctor about groups that can help you.

Who should be tested?

If you are thinking about having a child, experts recommend that:^{footnote 2}

• Both you and your partner get a screening test if you are both of Ashkenazi Jewish descent, or have a family history of the disease. If both of you test positive as carriers, genetic counselling may help you with making choices.
• You or your partner get a screening test if either of you is of Ashkenazi Jewish descent, has family from the Quebec Bas-St-Laurent or Gaspésie regions or New Brunswick territories, or has a family history of the disease. If one of you tests positive for being a carrier, the other partner should be tested.

Carriers of the Tay-Sachs gene changes can pass the changed gene to their children even though the carriers don't have the disease. If both you and your partner are carriers, there is a 1-out-of-4 chance (25%) that any child you have will have Tay-Sachs disease.