How Do People Get Tay-Sachs Disease?

Tay-Sachs disease is caused by a mutation (abnormal change) in the gene that codes for Hex-A. It is a recessive trait, which means that people will have the disease if they have two copies of the defective gene, but they will not have the disease if they have at least one unaffected copy. People with one normal copy and one defective copy are called carriers, because they can pass the disease on to their children.

Just about anyone can be a carrier of the gene for Tay-Sachs disease. In the general population, about 1 in 250 people carries the gene. However, some populations of people include more carriers than others. For example, 1 in 27 people of eastern European Jewish (Ashkenazi) descent in the United States is a carrier. People of French-Canadian ancestry from one part of Quebec and the Cajun population in Louisiana also have a higher than usual risk of carrying the Tay-Sachs gene.

Is There a Cure for Tay-Sachs Disease?

Although researchers look for a way to prevent or treat Tay-Sachs disease, as of 2009 no treatment or cure was known. However, tests have been developed that allow people to find out if they carry the defective gene. Blood tests can determine the level of Hex-A in people's blood (carriers have about half as much as noncarriers), and DNA tests may find evidence of mutations in the Hex-A gene. Testing is particularly useful for people who have had relatives with Tay-Sachs disease and for people in high-risk populations. Finding out about risk before having a baby can prevent an afflicted child from suffering and prevent the parental anguish of watching a child develop and then die from Tay-Sachs disease.

Prenatal tests also exist for women who already are pregnant. The amniotic fluid (the fluid in which the fetus develops) or the chorionic villus (structures inside the mother's uterus) both contain fluid from the developing baby that can be sampled and tested for the presence of Hex-A. If Hex-A is present, that means that the fetus does not have Tay-Sachs disease.

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