Chicago Center for Jewish Genetics Disorders - Ashkenazi Disorders: Tay-Sachs Disease

Ashkenazi Disorders: Mendelian

Tay-Sachs disease is the most familiar of the Jewish genetic disorders. Babies with Tay-Sachs disease are normal at birth. However, at 3-6 months of age, an affected baby will begin to lose developmental skills. Tay-Sachs disease is caused by a deficiency of an enzyme called hexosaminidase A or hex A. Lack of this enzyme affects the brain and the nervous system causing rapid and progressive deterioration. This condition is life shortening, with death usually occurring by the age of 6. No effective treatment is available at this time. A late-onset form of Tay-Sachs also occurs, although it is rare.

Disease frequency: Potentially 1in 3,600 in the Ashkenazi Jewish population. Frequency decreased through success of carrier screening programs.

Carrier frequency: 1/26 - 1/30 in Ashkenazi Jews, 1/300 in non-Jewish population.

Diagnosis: By measuring for deficiency of enzyme hex A in blood.

Inheritance: Autosomal Recessive

Carrier testing: By measuring for deficiency of hex A in blood and genetic testing of the Tay-Sachs gene. Testing detects approximately 98% of Ashkenazi Jewish carriers

Prenatal diagnosis: Possible by genetic testing of the Tay-Sachs gene or testing for deficiency of enzyme hex A. This testing is available to those with a previous affected child or to couples found to be at risk through carrier testing.

Late-onset Tay-Sachs disease

Late-onset Tay-Sachs disease (LOTSD) is caused by mutations in the same gene as classical infantile Tay-Sachs disease, HEXA, but the mutations cause less severe disease due to residual enzyme activity. There are three forms: juvenile, chronic, and adult onset. The distinction between these different forms is not clearly delineated and there is overlap.

Juvenile onset: Onset occurs between 2 to 10 years of age. These patients can live up to late childhood or adolescence. The symptoms are the same as those seen in classical TSD but occur at an older age and often progress more slowly. Optic atrophy and retinitis pigmentosa are often seen instead of the cherry red macula seen in classical TSD.

Chronic onset: Age of onset ranges from childhood to 10 years of age. The patients often have dysarthria, dystonia, choreoathetosis, ataxia, and a wide-based, unsteady gait. It may be mistaken for spinocerebellar ataxia, Friedreich ataxia, or amyotrophic lateral sclerosis. Progression is slow and lifespan is variable.

Adult onset: Age of onset is in adulthood. Patients may present with muscle wasting, weakness, fasciculations, and dysarthria. It may be mistaken for spinal muscular atrophy or early-onset amyotrophic lateral sclerosis. Up to 40% of patients have psychiatric manifestations such as recurrent psychotic depression, bipolar symptoms, and schizophrenia. It may be associated with dementia. Progression is slow and lifespan is variable.

Treatment: Current treatment is focused on managing the symptoms of LOTSD. Anticonvulsants, antidepressants, and antipsychotics may provide some relief.

Technical Information on Tay-Sachs Disease

Additional Information:
National Tay-Sachs and Allied Diseases Association
2001 Beacon Street, #204
Brighton, MA 02135
(800) 906-8723
fax: (617) 277-0134
email: ntsad-boston@worldnet.att.net
www.ntsad.org

Late-Onset Tay-Sachs Foundation
1303 Paper Mill Rd.
Erdenheim, PA 19038
(215) 836-9426
(800) 672-2022 (toll free)
email: mpf@bellatlantic.net
www.lotsf.org

Tay-Sachs and Allied Diseases Delaware Valley
101 Greenwood Avenue, Suite 570
Jenkintown, PA 19046
(215) 887-0877
fax: (215) 887-1931
email: NTSAD@aol.com
www.tay-sachs.org

National Tay-Sachs & Allied Diseases Association New York Area
1202 Lexington Avenue, #288
New York, NY 10028
(888) 354-7788 (toll free)
(212) 431-0431
fax: 888-354-4884
www.ntsad-ny.org

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This page last updated on September 7, 2007.