Interest has been expressed in the disease that has afflicted two of the three children of the rabbi and his wife who were just killed in the terrorist attacks in Mumbai. (The third child, a toddler of the age of two, was grabbed by his nanny and both of them managed to escape the massacre.)
The two other children were beset by the genetic disorder of Tay-Sachs Disease (or TSD). One of them died from the disease earlier this year. TSD is inherited in an autosomal recessive pattern. (Recessive genetic disorders occur when both parents are carriers and each contributes an allele to the embryo, meaning these are not dominant genes.) An increased prevalence in the Eastern European Jewish (Ashkenazi) population of this recessive allele was discovered in 1887. Historically, Eastern European people of Jewish descent (Ashkenazi Jews) have a high incidence of Tay-Sachs and other lipid storage diseases. In the United States, about 1 in 27 to 1 in 30 Ashkenazi Jews is a recessive carrier.
Infants with Tay-Sachs disease appear to develop normally for the first six months of life. Then, as nerve cells become distended with gangliosides (a fatty acid derivative), a relentless deterioration of mental and physical abilities occurs. The child becomes blind, deaf, and unable to swallow. Muscles begin to atrophy and paralysis sets in. Death usually occurs before the age of 4 or 5. There is currently no cure or treatment for TSD. Even with the best care, children with Infantile TSD die by the age of 5, and the progress of Late-Onset TSD can only be slowed, not reversed.
Genetic screening for carriers of Tay-Sachs disease is possible because an inexpensive enzyme assay test is available. Proactive testing has been quite effective in eliminating Tay-Sachs occurrence among Ashkenazi Jews. On January 18, 2005, the Israeli English language daily Haaretz reported that as a “Jewish disease” Tay-Sachs had almost been eradicated. Of the 10 babies born with Tay-Sachs in North America in 2003, none had been born to Jewish families. In Israel, only one child was born with Tay-Sachs in 2003, and preliminary results from early 2005 indicated that none were born with the disease in 2004.
In Orthodox Jewish circles, there is an organization (Dor Yeshorim) that carries out an anonymous screening program so that couples who are likely to conceive a child with Tay-Sachs or another genetic disorder can avoid marriage. It is possible that with the decrease in babies affected by the disease, testing has become less prevalent.
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While I applaud your accurate description of infantile and Late Onset Tay-Sachs I must note that Tay-Sachs has NOT be almost eradicated from the Jewish community. The gene remains a constant risk and it is only through education and screening incidence is reduced. It is also important to note that French Canadians and Louisianan Cajuns are also at high risk, those of British Isle/Irish descent have an increased carrier risk as high as 1/50 to as low as 1/150 while the general population is at risk at a rate of 1/250.
Another important aspect to consider is what constitutes a Jewish Tay-Sachs child? Is it a family that identifies themselves as Jewish or present one of the six common mutations associated with Ashkenazi Jews?
There are over 100 different mutations identified in the gene causing Tay-Sachs, only six are associated with Ashkenazi Jews.
Sincerely,
Kim Kubilus
Director of Member Services
National Tay-Sachs & Allied Diseases Association, Inc.
Thank you for your comment. I did not find incidence information on the website of your association. Besides the Israeli information cited above, I find that the U.S. National Institutes of Health calls the disease “rare,” and a study from The International TSD Data Collection Network carried out on an international data set from 1970-1993 found only 16 instances out of 2416 “at risk” pregnancies that were evaluated (JAMA 1993 Nov 17; 270(19):2307-15). This is not to minimize the heartbreak of the disease for those who do contract it, or who have to endure seeing a loved one develop the disease. If you have other incidence data, it would be most interesting if you would share it.
Hello!
Tay-Sachs is a rare disease but the gene is not. The only way to continue to low incidence of the disease is through vigilance and constant awareness of the risks.
The gene carrier rates are found on this page:
http://www.ntsad.org/S06/S06TScarrier.htm
Thank you!
Kim
Kim,
Yes, thank you for making clear that emphasis should be placed on the distinction between the disease and the gene!
rhapsodyinbooks
[...] For more information on Tay-Sachs Disease, see my earlier post here. [...]
This topic is quite hot in the net at the moment. What do you pay attention to while choosing what to write about?