Tay-Sachs Disease - Topic Overview
What is Tay-Sachs disease?
Tay-Sachs is a rare disease that is passed down through some families. It harms the brain and nerve cells. There are two forms:
- The most common form develops soon after a baby is born. The child usually lives for 4 or 5 years.
- 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 does not have Tay-Sachs disease.
What causes Tay-Sachs disease?
Tay-Sachs can occur when parents pass on a changed (mutated) 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 carry the changed gene but will not have the disease.
The changed gene keeps your body from making an enzyme called hexosaminidase A (hex A). Hex A breaks down normal fatty compounds (called gangliosides) in cells. When these fatty compounds are not broken down, they build up and damage brain and nerve cells, causing Tay-Sachs disease.
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, 2 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, lose his or her vision, and not be able to move.
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 Tay-Sachs disease diagnosed?
WebMD Medical Reference from Healthwise
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