What causes Tay-Sachs disease?

Children with Tay-Sachs disease have no working version of a gene that makes a particular enzyme called hexoaminidase-A (Hex-A). This enzyme normally breaks down excess fatty substances in the nerve cells. Without it, fats build up and eventually destroy the nerve cells of the affected child. This process starts in the embryo, but is not noticeable until the baby is between 6 and 9 months old. Carriers of Tay-Sachs only have half the normal levels of Hex-A in their bodies, but they are not affected by the condition.

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Sheila and Philip Koch had two children who died of Tay-Sachs disease in the 1960s. Dr Koch later developed the enzyme test to detect unaffected carriers of the condition.

How is Tay-Sachs disease inherited?

Tay-Sachs disease affects children who inherit two copies of an altered gene from their carrier parents. Carriers of Tay-Sachs disease are not affected themselves, because they have a working gene as well as an altered one. Carrier parents have a one-in-four chance of having an affected child, a one-in-two chance of having a child who is an unaffected carrier and a one-in-four chance of having a child who doesn't carry any altered genes.

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Inheritance of Tay-Sachs disease.

Is there a test for Tay-Sachs disease?

Tay-Sachs disease is most common in people of Central and Eastern European Jewish descent. In this community, one in 25 people are carriers of Tay-Sachs disease, compared with one in 250 of the non-Jewish population. They are not affected by the condition, and most would never know they are carriers. But, because the disorder is so devastating, doctors offer a carrier test to high-risk communities in the UK. The test results can help carriers make decisions when planning a family.

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Doctors offer a Tay-Sachs carrier test to high-risk communities in the UK.

 

Principal Funder:

Wellcome trust

Major Sponsors:

GlaxoSmithKline life technologies