Pregnancy Termination: Tay Sacks Disease

The tragedy of a Tay-Sacks baby is that at birth and for the first few months the baby seems entirely healthy. The child's health gradually deteriorates with progressive destruction of the nervous system leading to physical and mental problems, including paralysis, blindness and generalised debility until the child dies usually before the age of four.

A Tay-Sacks baby cannot produce an enzyme called hexosaminidase. This enzyme is an essential catalyst in the body's breakdown of a group of chemicals called mucopoly-saccharides.

Q19.3B We have no family history of Tay-Sacks. Why should we consider screening?

The majority of babies afflicted by Tay-Sacks are born into families who have no history of the condition.

Q19.3C How prevalent is Tay-Sacks Disease?

Approximately 1 baby in 2,250 born to couples of Eastern European Jewish (Ashkenazi) descent is born with Tay-Sacks Disease. This compares to an incidence in the rest of the population of 1:225,000 and one in 22,500 where one parent is Jewish.

Q19.3D If we are healthy, how can we possibly transmit the disease to our child?

A Tay-Sacks baby cannot produce an enzyme called hexosaminidase. This enzyme is an essential catalyst in the body's breakdown of a group of chemicals called mucopoly-saccharides.

Tay-Sacks is an auto-somal recessive condition; the affected child must have received the abnormal gene from both parents. Carriers of the condition have one normal and one abnormal gene and they have enough hexosaminidase to function normally.

Q19.3E What are the chances of us having child affected with Tay-Sacks disease?

A Tay-Sacks baby cannot produce an enzyme called hexosaminidase. This enzyme is an essential catalyst in the body's breakdown of a group of chemicals called mucopoly-saccharides.

In the Ashkenazi population, 1 in 25 individuals are carriers for Tay-Sacks. This results in one couple in 625 with both partners being carriers. As each partner of carrier couples has a 1 in 2 chance of giving the abnormal chromosome to their child, 1 in 4 of their children statistically are likely to have the disease; 1 in 2 of their children will be carriers and 1 in 4 will have entirely normal hexosaminidase genes.

Q19.3F Can Tay-Sacks Disease be prevented?

A Tay-Sacks baby cannot produce an enzyme called hexosaminidase. This enzyme is an essential catalyst in the body's breakdown of a group of chemicals called mucopoly-saccharides.

There is no treatment available for an affected child. For those couples with both partners known to be carriers, tests can be performed in early pregnancy. If the test proves to be positive then there is an option for the pregnancy to be discontinued.

Q19.3G When should screening be considered?

A Tay-Sacks baby cannot produce an enzyme called hexosaminidase. This enzyme is an essential catalyst in the body's breakdown of a group of chemicals called mucopoly-saccharides.

Ideally, screening should be performed before pregnancy and some would advocate before marriage. Only one partner requires screening and if negative then there is no chance of the child having the disease. Should the first partner prove to be positive then the second partner requires screening.

Counselling should be offered to at risk couples when they seek advice before contemplating a pregnancy, for example when re questing contraception, or fertility investigation and during early antenatal care.

The author has counselled many at risk couples and recently found a husband and wife who were both carriers for the disease. Typically, there was no relevant family history. Unfortunately, the fetus tested positive for the disease and, at the couples re quest, the pregnancy was terminated. There were no problems in the next pregnancy.

Q19.3H How is screening undertaken.

A Tay-Sacks baby cannot produce an enzyme called hexosaminidase. This enzyme is an essential catalyst in the body's breakdown of a group of chemicals called mucopoly-saccharides.

In the London area, a blood sample is sent by the local laboratory to Guy's Hospital.

Screening tests are discussed inscreening tests

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