Causes Of Tay-Sachs Disease

Tay-Sachs disease is an autosomal recessive disease that affects the lysosome storage in cells. Over time, the disease deteriorates the functions of the body leading to blindness, deafness, dementia, and recurrent convulsions in the terminal stages. Unfortunately, its main victims are children, who often show the first signs and symptoms at around 6 months old and usually do not live past the age of 5. There is also a juvenile and late-onset form that may not appear until the second or third decade of life. By the year 1993 (American Medical Association), geneticists were able to identify that the cause of this disease is triggered by a mutation in the HEXA gene, located at 15q23-q24, which codes for the hexosaminidase A enzyme. Without this
Among Ashkenazi Jews, 1 in every 29 individuals is heterozygous (asymptomatic) for Tay-Sachs disease causing mutations. Following the development of prenatal diagnosis for Tay-Sachs disease in the early 1970’s, most couples who had had an affected child chose to monitor later pregnancies and bring to term only pregnancies of unaffected fetuses. Since only couples with a previous affected child could be aware of their risk, carrier screening programs were hugely initiated in the high-risk populations, aiming at detecting and informing carrier couples prior to any family history of the disease. Up to 1992, over one million individuals had been tested for Tay-Sachs disease carrier status, more than 36,000 carriers had been detected and 1,054 carrier couples had been identified and informed of their risk prior to having an affected child. These programs led to a 90% decrease in the incidence of Tay Sachs disease in the Ashkenazi Jewish populations in the USA, Israel and Canada. Molecular diagnosis for Tay-Sachs disease in specific populations has presented an alternative way for performing enzymatic testing in detecting
All the carriers were of Ashkenazi Jewish ancestry. This indicated a carrier frequency of 1 in every 51 students, similar to that observed in several Jewish populations. The carrier frequency was separated by state, and found 7 carriers among 258 participants in São Paulo and 1 carrier among 146 participants in Rio de Janeiro. The estimated carrier frequency for Tay-Sachs disease is 1 in 33 (8/263), similar to that observed in other Ashkenazi Jewish populations. During the study, three carriers contacted the lab for re-testing and additional counseling. The mother of a carrier was also identified as a carrier, and the carrier frequency between the two cities was not significant. Based on the data, this shows how unaware the Jewish people of Brazil were to the importance of getting screened. The data was so significant that a few people even felt the need to continue to get even more tests done.
Preconception genetic screening programs for TSD have been introduced in Jewish communities worldwide to determine individuals’ carrier status. Australian genetic screening programs for TSD have targeted senior Jewish high school students in Sydney (from 1995 to 2012) and in Melbourne (from 1998 to 2011). Sydney and Melbourne are home to Australia’s two largest Jewish communities, where 50%–70% of Jewish high school students attend schools that access screening. An important measure of the success of a genetic screening program is