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Genetic Diseases

What is tay-sachs Disease?

The classical form of Tay-Sachs Disease (TSD) is a fatal genetic disorder in children which progressively destroys the central nervous system. It is caused by the absence of a vital enzyme, Hex-A. A baby with TSD appears to develop normally for the first few months, then there is a relentless deterioration of mental and physical abilities. The child gradually becomes blind, is unable to swallow, and has inefficient pulmonary function. Muscles begin to atrophy, paralysis sets in, and response to the environment diminishes. There is no cure or treatment and average life expectancy is 3-5 years of age.

Late-onset Tay-Sachs disease (LOTS) is a variant of Tay-Sachs but less common than the infantile form. As the name suggests, LOTS affects older children and adults rather than infants, and manifests itself as a more slowly progressive loss of functioning of the nervous system than the infantile form. Individuals with LOTS have a small residual amount of Hex-A rather than a complete absence of the enzyme. In fact, Tay-Sachs disease has a continuum of severity based on the amount of residual Hex-A activity present in the cells.

Recessive diseases such as Tay-Sachs often occur more frequently, though not exclusively, in a defined population. Tay-Sachs affects several ethnic populations,in addition to the Jewish population. Every person of Jewish, French-Canadian, Cajun or Irish heritage should be tested for Tay-Sachs carrier status. One in 25 Ashkenazic Jews (from Eastern or Central European descent), French-Canadians or Cajuns carry the Tay-Sachs gene. Current research estimates that as many as one in 50 Irish-Americans to one in 190 are carriers; and one in 250 of the general population are carriers of the Tay-Sachs gene. Carrier screening involves analysis of the enzyme responsible for Tay-Sachs disease, as well as DNA analysis to determine the mutation.