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Tay-Sachs, Canavan, Sandhoff, GM1 and related diseases

Tay-Sachs Carrier Screening

Tay-Sachs disease most often affects families with no known history of the disease. A mutation in the HEXA gene can be carried silently through many generations. Carrier screening enables prospective parents to understand the risk of passing on an inherited genetic condition such as Tay-Sachs disease to their children. Carrier screening prior to pregnancy is most advantageous, as it enables a couple to do research, seek resources, and make an informed decision while having the greatest number of reproductive options.

Tay-Sachs disease carriers are more frequently from Ashkenazi Jewish, French Canadian, Pennsylvania Dutch, Irish, and Cajun backgrounds. However, anyone can be a carrier. Be sure to discuss your ancestry with your genetics provider so that appropriate carrier screening is ordered.

Genetic counseling is strongly recommended prior to carrier screening. A genetic counselor can explain testing options, interpret test results, facilitate decision making, and assist with insurance coverage. For more information about how to contact a genetic counselor, visit the Genetic Counseling tab.

 

Enzyme Screening:

Enzyme screening is currently the gold standard for Tay-Sachs disease carrier screening. It is performed using an enzyme assay which detects the level of protein produced in the blood from the HEXA gene for Tay-Sachs. Enzyme assays can be performed using serum or leukocytes isolated from blood. Serum is most commonly used but leukocyte screening is recommended when the person screened is pregnant, taking birth control pills, or on any medications that affect hormones.

The enzyme measured in Tay-Sachs disease screening is called Hexosaminidase A. Individuals with infantile onset Tay-Sachs are expected to have absent or nearly absent Hexosaminidase A enzyme activity while those with juvenile or adult onset Tay-Sachs disease tend to have 6-15% Hexosaminidase A enzyme activity.

 

Molecular Genetic Screening:

Genetic carrier screening for Tay-Sachs disease can also be performed by reading across both copies of one’s HEXA genes and detecting if there are any known changes (mutations). A negative (normal) result significantly reduces the chance of being a carrier, but it does not eliminate the chance. It is possible to carry a mutation that has not yet been discovered or that our current technology is unable to detect.   It is also possible to receive an “uncertain” result called a “variant of uncertain significance” (VUS). This means that a change was found in the spelling of the HEXA gene but it is not yet known if that change is normal human variation or if it denotes carrier status. It is important to discuss how a VUS result may impact your family’s health with a genetic professional.  

 

NOTE: A combination of genetic and enzyme testing is strongly recommended for Tay-Sachs screening for the most sensitive results. View the NTSAD Position Statement on Tay-Sachs Screening

 

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