Tay-Sachs Disease: A Genetic Disorder Associated with the Jewish Population

Tay-Sachs disease is a fatal, inherited genetic disorder that is caused by an abnormal gene passed to the child from both parents. Most commonly, Tay-Sachs disease is seen among the Jewish population. It is estimated that 1 in every 27 to 30 Jewish people are carriers of the gene that causes Tay-Sachs, while 1 in every 250 non-Jewish people are carriers. While this is true, Tay-Sachs disease is also seen more among non-Jewish French Canadians living near the St. Lawrence River as well as in the Cajun community of Louisiana. These people have the same carrier rate, 1 in 27 to 30 people, as those of Jewish decent. Those people who have ancestors from Ireland, the Irish American community, also have a higher carrier rate than the general population, at 1 in 50.

Tay-Sachs disease is caused by defects in a gene on the 15^th chromosome. This defective gene is responsible for the production of the Hex-A enzyme. If one or both of the Hex-A genes are active in the bodies cell, the body is able to produce enough of the enzyme to prevent the abnormal build-up of what is known as the GM2 ganglioside lipid, a fatty material present in the body. Without this enzyme, this fatty material builds up in the brain, and eventually damages nerve cells and causes neurological problems. Those who carry the gene have only one copy with the active gene and appear to be healthy. These people do not have Tay-Sachs disease but can potentially pass the disease on to their offspring. When both parents are carriers, there is a 25% chance for their offspring to have the disease, a 50% chance for their offspring to be a carrier, and a 25% chance that the child will neither have Tay-Sachs disease nor be a carrier.

There are two types of Tay-Sachs disease. The first, and most common type develops soon after a baby is born. The baby appears normal until about the age of 3 to 6 months. At this time, development begins to slow and the parent or caregiver may notice that the baby makes less eye contact and has a hard time focusing his or eyes on objects. The doctor may notice a red spot on the baby's retina. From 6 to 10 months of age, the parent or caregiver may notice that the baby does not seem as alert and playful as he or she has been. The baby may have a hard time sitting up or rolling over. The baby may also show signs of impaired vision and/or hearing. At the age of 10 months or older, Tay-Sachs diseases quickly worsens. By the age of 2 years old, most affected children begin having seizures and decreased mental functions. There is a gradual regression, and eventually, the child can no longer crawl, roll-over, sit up, or reach for things. Eventually, Tay-Sachs disease leads to blindness, loss of cognitive abilities, paralyzed, and unresponsive. By the time a child with Tay-Sachs disease reaches the age of 3 or 4 years old, the nervous system is so badly effected that death occurs by the age of 5 years old.

The second type of Tay-Sachs disease is much more rare and known as Late-Onset Tay-Sachs disease (LOTS). This type generally develops between adolescence and the mid-30s. In this type of Tay-Sachs disease, early symptoms often go unnoticed because to many people they seem normal. Such symptoms include clumsiness and mood changes. Later symptoms include things such as muscle weakness and twitching, slurred speech, and trouble thinking and reasoning. The symptoms depend upon how much Hex-A the body produces. The less the body produces, the worse the symptoms are.

Diagnosis of Tay-Sachs disease includes a physical exam and a blood test to determine the amount of Hex-A in the blood. If there is any question as to whether the person has Tay-Sachs disease after these tests, a genetic test can be performed to make a definitive diagnosis.

Currently, there is no cure for Tay-Sachs disease. Treatment focuses on keeping the affected person as comfortable as possible as managing the symptom. Supportive measures may be taken to help the family cope with the diagnosis. Individual counseling, grief counseling, and many other supportive groups are available to help those affected by the diagnosis better cope. For those diagnosed with late-onset Tay-Sachs disease, it will be necessary to have a living well as a durable power of attorney.

In order to prevent Tay-Sachs disease, it is advised that anyone who has a high chance of carrying the disease to have genetic testing. If it is shown that both parents carry the gene, they need to completely know the risks and chances of having a child with Tay-Sachs disease. If both parents are carriers and the woman is pregnant, tests can be done to determine whether or not the baby has the disease. Amniocentesis and chronic villli sampling are two available tests to determine whether or not the baby has the disease.

If testing has not previously been done and any child or adult begins displaying neurological problems, they should be completely evaluated by a doctor.

Sources for this article include:

http://www.tay-sachs.org/taysacchs_disease.php
http://www.cigna.com/healthinfo/hw182975.html
http://www.intelihealth.com/IH
http://www.genome.gov/pfv.cfm?pageID=10001220