Tay-Sachs disease

Overview

What is Tay-Sachs disease?

Tay-Sachs disease is a rare neurological disorder. Individuals with this disorder cannot break down a normal substance in the body called GM2 ganglioside, a type of fatty material called a lipid. Because they can't break this substance down, it builds up in cells of the body, particularly nerve cells in the brain and spinal cord. When enough of this fatty material builds up, it destroys the cells and damages the surrounding tissue. The most common form of Tay-Sachs disease is the early infantile form. The first sign is often an exaggerated startle response, which means when an infant is startled the reaction is disproportionate to whatever startled him or her. Infants will eventually lose previously acquired skills like the ability to sit up or hold up their head. As they age, additional symptoms can develop including seizures, vision problems, hearing loss and intellectual disability. Eventually, children will become less aware of their surroundings and voluntary movements will decrease. Death usually occurs around four years of age. Tay-Sachs disease is caused because people have a change or alteration (mutation) in both their HEXA genes. This gene produces an enzyme that is needed to break down GM2 ganglioside. Tay Sachs is inherited in an autosomal recessive manner, which means that a child inherits one altered HEXA gene from each parent.

References
  • Kaback MM, Desnick RJ. Hexosaminidase A Deficiency. GeneReviews website. Accessed September 20, 2016. http://www.ncbi.nlm.nih.gov/books/NBK1218/
  • Tay-Sachs Disease. The National Organization for Rare Disorders website. Accessed September 20, 2016. http://rarediseases.org/rare-diseases/tay-sachs-disease/
  • Tay-Sachs disease. Genetics Home Reference website. Accessed September 20, 2016. https://ghr.nlm.nih.gov/condition/tay-sachs-disease
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Are there other names for Tay-Sachs disease?

How common is Tay-Sachs disease?

What are the subtypes of Tay-Sachs disease?

Are there other names for Tay-Sachs disease?

There are several different names doctors may use for Tay-Sachs disease. However, the most common name for this disorder is Tay-Sachs disease. Other names that may be used to describe this disorder include:

  • GM2 Gangliosidosis, Type 1
  • B Variant GM2-Gangliosidosis
  • Hexosaminidase A Deficiency
  • HEXA deficiency
  • TSD
References
  • Tay-Sachs disease. Online Mendelian Inheritance in Man (OMIM) website. Accessed September 20, 2016. http://omim.org/entry/272800
  • Tay-Sachs Disease. The National Organization for Rare Disorders website. Accessed September 20, 2016. http://rarediseases.org/rare-diseases/tay-sachs-disease/
How common is Tay-Sachs disease?

Tay-Sachs disease is a rare disorder. Rare disorders often go unrecognized or misdiagnosed and the incidence and prevalence of individual rare disorders is often unclear or unknown. Prevalence is the measurement of all individuals affected by the disease at a particular time. Incidence is the number of new people with a disorder or newly-diagnosed. Tay-Sachs disease occurs more often in certain ethnic groups. The carrier rate in people of Ashkenazi Jewish descent is about 1 in 30. The Ashkenazi are people who are descended from certain Jewish people who lived in Central and Eastern Europe. Other ethnic groups with higher than average carrier rates for Tay-Sachs disease include certain French Canadians near Quebec, Cajuns from Louisiana, and some Old Order Amish people in Pennsylvania.

The overall carrier rate is estimated to be in 1 in 250 people in the general population as a whole. The overall incidence and prevalence rates are not known.

References
  • Kaback MM, Desnick RJ. Hexosaminidase A Deficiency. GeneReviews website. Accessed September 20, 2016. http://www.ncbi.nlm.nih.gov/books/NBK1218/
  • Tay-Sachs disease. Genetics Home Reference website. Accessed September 20, 2016. https://ghr.nlm.nih.gov/condition/tay-sachs-disease
What are the subtypes of Tay-Sachs disease?

The different forms of Tay-Sachs disease are:

  • Classic Tay-Sachs disease - Also called infantile Tay-Sachs disease, this form is the most common form of the disorder. Symptoms usually begin around 3-6 months of age. The disorder is often fatal by the age of 4.
  • Juvenile Tay-Sachs disease - Also called subacute Tay-Sachs disease, the juvenile form is extremely rare. These children have later onset of symptoms than do infants with the classic form. The symptoms get worse at a slower rate and the neurological symptoms can vary greatly from one child when compared to another. These children can survive until later in children or adolescence.
  • Adult Tay-Sachs disease - This form of Tay-Sachs disease is variable. This means how the disorder affects one person when compared to another can be very different. Symptoms can be seen as early as 10, but usually the disorder is not diagnosed until adulthood. Sometimes life-threatening complications develop.
References
  • Kaback MM, Desnick RJ. Hexosaminidase A Deficiency. GeneReviews website. Accessed September 20, 2016. http://www.ncbi.nlm.nih.gov/books/NBK1218/
  • Baumann N, Turpin J. Tay-Sachs disease. OrphaNet website. Accessed September 20, 2016. http://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=EN&Expert=845

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