| Tay-Sachs is an autosomal recessive (genetic) disease of children, that
occurs when two carriers of the recessive trait (affects one of the gene
pair, but not both) and produce a child with both genes present. It is most
commonly found among offspring of Ashkenazi Jewish ancestry.
The disease occurs because of an inability of the gene to produce an
enzyme, "hexosaminidase A." (or "Hex A)
If only one of the gene pair is unable to produce Hex A, the other gene
can produce enough to keep the person normal, but that person remains a
"carrier" for the Tay-Sachs gene or disease.
If a carrier produces a baby with a non-carrier, at worst, the child
might also be a carrier, but will not have the disease, because it takes two
abnormal genes (one from the father and one from the mother) to produce this
disease.
If two carriers produce a child, then the outcome may include a totally
normal child, a Tay-Sachs carrier, or a child with Tay-Sachs disease.
If both prospective parents are tested negative prior to pregnancy, they
can be reassured that there is little risk for Tay-Sachs disease. If one
parent tests positive, but the other is negative, they can be reassured that
there is little risk of Tay-Sachs disease, but the child may be born a
carrier for the trait. If both prospective parents test positive for the
trait, then the greatest likelihood is that the baby will be born with the
trait, but that there is also a significant chance the baby will have Tay-Sachs
disease (or be normal, without the trait).
If testing is performed during pregnancy, a complication arises, in that
pregnancy can make the test in the woman less reliable. For that reason,
during pregnancy, this testing is usually performed just on her partner.
When negative (and it usually is), no further testing is needed as the child
will not have Tay-Sachs disease if the father of the child is not a carrier. |
Normal Values*
| Tay-Sachs Screen
(Hex A) |
Negative |
*These are general values taken from a variety of
sources. The actual normal values may vary from lab to lab and from one
type of testing protocol to another. |
