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Diseases

Genetic and Rare Diseases Information Center (GARD)

Sandhoff disease


Other Names for this Disease
  • Beta-hexosaminidase-beta-subunit deficiency
  • GM2 gangliosidosis, type 2
  • Total hexosaminidase deficiency
  • Hexosaminidase A and B deficiency Disease
  • Sandhoff-Jatzkewitz-Pilz disease
Related Diseases
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.

Tests & Diagnosis

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Can you provide information about carrier testing for Sandhoff disease?

Carrier testing is performed to identify individuals who have a gene mutation and may be at risk for having a child or other family members with the same mutation. Carriers usually do not have symptoms related to the gene mutation. Carrier testing is typically offered to individuals who have family members with a genetic condition, family members of an identified carrier, and individuals in ethnic or racial groups known to have a higher carrier rate for a particular condition.[1]

There two types of carrier screening tests: DNA and biochemical. Sandhoff carrier screening is available through DNA or biochemical testing. DNA carrier screening detects specific known mutations that are ‘looked’ for in the test. A negative DNA carrier result does not eliminate an individual's chances of being a carrier because of the possibility of carrying an unknown mutation or one not ‘looked’ for in the test. Biochemical testing, also called an enzyme assay, detects the level of the enzyme(s) in question in the blood. Enzyme assays can be done using serum or leukocytes (white blood cells). Serum is typically the standard test, but leukocyte testing is recommended when the person being tested is pregnant, on birth control pills or taking any medications that affect hormones because all of these situations can potentially interfere with the accuracy of the serum test. DNA carrier screening may be recommended if the results of the biochemical test are uncertain.[2]

Sandhoff disease is associated with deficiencies of both hexosaminidase A (hex A) and hexosaminidase B (hex B) enzyme activity. Carriers of Sandhoff disease have reduced (but adequate) amounts of both hex A and hex B. While most hex A assays are performed to identify Tay-Sachs carriers, the test also can also identify individuals that are carriers of Sandhoff disease. Looking at the total hexosaminidase activity in combination with the percent of hex A activity present can aid in determining whether an individual is a carrier of Sandhoff disease. Typically, a decreased amount of total hexosaminidase activity along with an increase in the proportion of hex A activity in leukocytes is suggestive of a Sandhoff carrier.[3] In contrast, Tay-Sachs carriers have a decrease in the amount of hex A activity. When the hex A enzyme result indicates that an individual is a possible Sandhoff carrier, the next step is typically to offer carrier testing to the individual's partner. If the partner is negative, the risk for the couple to have a child affected with the disorder is very significantly decreased. If the partner is also a possible carrier, more comprehensive testing may be offered.

We are unable to make recommendations about genetic screening and/or testing, but we do recommend genetic counseling for questions about carrier and prenatal genetic screening. Genetic counselors are non-directive healthcare professionals that help individuals understand their options. Genetic counselors are very knowledgable about testing guidelines and procedures. They can help a person to understand the tests and what the results mean for individuals, partners, children and extended family members.[4]
Last updated: 8/22/2011

References
  1. Uses of Genetic Testing. GeneTests. March 19, 2004; http://www.ncbi.nlm.nih.gov/projects/GeneTests/static/concepts/primer/primerusesof.shtml#carrier. Accessed 8/22/2011.
  2. Types of Screening. National Tay-Sachs & Allied Diseases. http://www.ntsad.org/index.php/carrier-screening/types-of-screening. Accessed 8/22/2011.
  3. Hexosaminidase A and Total Hexosaminidase, Leukocytes. Mayo Clinic-Mayo Medical Laboratories. http://www.mayomedicallaboratories.com/test-catalog/Overview/8775.
  4. Genetic Counseling. National Tay-Sachs & Allied Diseases. http://www.ntsad.org/index.php/family-planning/genetic-counseling. Accessed 8/22/2011.


Testing

  • The Genetic Testing Registry (GTR) provides information about the genetic tests for this condition. The intended audience for the GTR is health care providers and researchers. Patients and consumers with specific questions about a genetic test should contact a health care provider or a genetics professional.
Other Names for this Disease
  • Beta-hexosaminidase-beta-subunit deficiency
  • GM2 gangliosidosis, type 2
  • Total hexosaminidase deficiency
  • Hexosaminidase A and B deficiency Disease
  • Sandhoff-Jatzkewitz-Pilz disease
Related Diseases
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.