Healthy babies develop vision, movement, hearing, and other vital
functions in part because enzymes clear out fatty protein and other
unwanted material that can interfere with growth.
But a baby with Tay-Sachs disease is born without one of those
important enzymes, Hexosaminidase A (Hex A). So, as those fatty
proteins build up in the brain, they hurt the baby's sight,
hearing, movement, and mental development.
A child can only get Tay-Sachs by inheriting it. The genetic
trait is relatively common among certain ethnic groups, such as
Ashkenazi Jews. Tay-Sachs can be detected before birth, so couples
in at-risk ethnic groups who are thinking of having children may
want to get a blood test to find out whether their child would be
likely to have it.
Who Is at Risk for Tay-Sachs?
Each year, about 16 cases of Tay-Sachs are diagnosed in the
United States. Although Ashkenazi Jews (Jews of central and eastern
European descent) are at the highest risk, it is now also prevalent
in non-Jewish populations, including people of
French-Canadian/Cajun heritage.
Some people carry the genetic mutation that causes Tay-Sachs,
but do not develop the full-blown disease. Among Ashkenazi Jews, 1
in 27 people are carriers; in the general population, 1 in 250
people are.
A child can only have Tay-Sachs disease if both parents are
carriers of the gene. When two carriers have a child together,
there's a:
- 50% chance that their child will be a carrier, but not have
the disease
- 25% chance that their child will not be a carrier and not
have the disease
- 25% chance that their child will have the disease
Screening
Couples who are considering having children - or are already
expecting - can get screened for the Tay-Sachs gene with a simple
blood test. If both the mother and father carry the Tay-Sachs gene,
an obstetrician/gynecologist may refer the couple to a genetic
counselor for more information.
Prenatal Diagnosis
Pregnant mothers can have their unborn babies tested for the Hex
A deficit that causes Tay-Sachs disease. (If the tests do not
detect Hex A, the infant will have Tay-Sachs disease. If the tests
do detect Hex A, the infant won't have it.)
Between the 10th and 12th weeks of pregnancy, an expectant
mother can get a chorionic villus sampling, or CVS, in which a
small sample of the placenta is drawn into a needle or a small tube
for analysis.
Between the 15th and 18th weeks of pregnancy, the mother can
have an amniocentesis to test for the Tay-Sachs gene. In this test,
a needle is inserted into the mother's belly to draw a sample
of the amniotic fluid that surrounds the fetus.
Signs and Symptoms
Kids are usually tested for Tay-Sachs after having hearing,
sight, and movement problems. A doctor can identify the disease
with a physical exam and blood tests.
A baby born with Tay-Sachs develops normally in the first 3 to 6
months of life. During the next months - or even years - the baby
will progressively lose the ability to see, hear, and move. A red
spot will develop in the back of the child's eyes. The child
will stop smiling, crawling, turning over, and reaching out for
things. By the age of 2, the child may have seizures and become
completely disabled. Death usually occurs by the time the child is
5 years old.
In rare forms of the disease, a child may have the Hex A enzyme,
but not enough of it to prevent developmental problems. In one of
these forms, called Juvenile Hex A Deficiency, those problems may
not appear until the child is 2 to 5 years old. The disease
progresses more slowly, but death usually occurs by the time the
child is 15 years old. In another, milder form of Tay-Sachs, the
disease causes muscle weakness and slurred speech, but sight,
hearing, and mental capabilities remain intact.
Helping a Child With Tay-Sachs
There is no cure for any form of Tay-Sachs disease. But doctors
may be able to help a child with Tay-Sachs cope with the symptoms
of the disease by prescribing medication to relieve pain, manage
seizures, and control muscle spasticity.
Researchers are studying ways to improve treatment for Tay-Sachs
disease and screening methods for the disease.
If your child has been diagnosed with Tay-Sachs or both you and
your partner are carriers of the gene, talk to your doctor or a
genetic counselor about ongoing research. You also might seek
support from a group such as the National Tay-Sachs and Allied
Diseases Foundation or the March of Dimes Birth Defects
Foundation.
Reviewed by:
Louis E. Bartoshesky, MD, MPH
Date reviewed: October 2008
Note: All information is for educational purposes only. For specific medical advice,
diagnoses, and treatment, consult your doctor.
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