Tay-Sachs disease


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Tay-Sachs disease

(tā`-săks`), rare hereditary disease caused by a genetic mutation that leaves the body unable to produce an enzymeenzyme,
biological catalyst. The term enzyme comes from zymosis, the Greek word for fermentation, a process accomplished by yeast cells and long known to the brewing industry, which occupied the attention of many 19th-century chemists.
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 necessary for fat metabolism in nerve cells, producing central nervous systemnervous system,
network of specialized tissue that controls actions and reactions of the body and its adjustment to the environment. Virtually all members of the animal kingdom have at least a rudimentary nervous system.
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 degeneration. The disease is named for a British ophthalmologist, Warren Tay, who first described the disease, in 1881, and a New York neurologist, Bernard Sachs, who first described the cellular changes and the genetic nature of the disease, in 1887. In infants, it is characterized by progressive mental deterioration, blindness, paralysis, epileptic seizures, and death, usually between ages three and five. Late-onset Tay-Sachs occurs in persons who have a genetic mutation that is similar but allows some production of the missing enzyme. There is no treatment for Tay-Sachs.

Course of the Disease

The enzyme involved in Tay-Sachs is called hexosaminidase A. Its absence allows a lipid called GM2 ganglioside to build up in the brain, destroying the nerve cells. The process starts in the fetus; the disease is clinically apparent in the first few months of life. Initial symptoms vary, but usually include a general slowing of development and loss of peripheral vision. By the age of one, most children are experiencing convulsions. The damage to the nervous system progresses inexorably, bringing with it an inability to swallow, difficulty in breathing, blindness, mental retardation, and paralysis.

In late-onset Tay-Sachs, which is often misdiagnosed, the symptoms (ataxia, dysarthria, and muscle weakness) usually become apparent late in childhood or early in adulthood. About 40% of the patients display symptoms of bipolar disorderbipolar disorder,
formerly manic-depressive disorder
or manic-depression,
severe mental disorder involving manic episodes that are usually accompanied by episodes of depression.
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. Life expectancy does not appear to be affected.

Genetic Basis and Screening

Tay-Sachs disease occurs primarily among Jews of Eastern European descent but is also found in French Canadians whose roots are in the St. Lawrence region, certain Cajuns in Louisiana, and some Amish communities. Tay-Sachs is an autosomal recessive disorder; a person must have two defective genes (one from each parent) in order for the disease to occur. Carriers, people with only one gene for the disorder, are physically unaffected. When both parents are carriers, each child has a 25% chance of getting the disease. If only one parent is a carrier, there is no chance that the child will get the disease, but there is a 50% chance that the child will be a carrier. The gene may be carried by many generations without a manifestation. For this reason, plus the historical lack of accurate diagnosis and routinely high infant mortality of past generations, there is often no known family history of the disease.

Genetic screening (see genetic testinggenetic testing,
medical screening for genetic disorders, by examining either a person's DNA directly or a person's biochemistry or chromosomes for indirect evidence. Testing may be done to identify a genetic disorder a person has, whether the disorder is already evident or not,
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) for the disease has been possible since the early 1970s and is encouraged in high-risk populations. Blood tests of carriers reveal a reduced amount of the hexosaminidase A. If a couple elects to go forward with a pregnancy, fetal status (again utilizing hexosaminidase A levels) can be ascertained via chorionic villus samplingchorionic villus sampling
(CVS) or chorionic villus biopsy
(CVB) , diagnostic procedure in which a sample of chorionic villi from the developing placenta is removed from the uterus of a pregnant woman (see pregnancy) using a fine needle inserted through the abdomen or
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 or amniocentesisamniocentesis
, diagnostic procedure in which a sample of the amniotic fluid surrounding a fetus is removed from the uterus by means of a fine needle inserted through the abdomen of the pregnant woman (see pregnancy).
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. Genetic screening and counseling has greatly reduced the incidence of the disease.

Bibliography

See M. M. Kaback, ed., Tay-Sachs Disease: Screening and Prevention (1977); W. Stockton, Altered Destinies (1979).

Tay-Sachs disease

[¦tā ¦saks di‚zēz]
(medicine)
A form of sphingolipidosis, transmitted as an autosomal recessive, in which there is an accumulation in neuronal cells of the neuraminic fraction of gangliosides; manifested clinically within the first few months of life by hypotonia progressing to spasticity, convulsions, and visual loss accompanied by the appearance of a cherry-red spot at the macula lutea. Also known as infantile amaurotic familial idiocy.
References in periodicals archive ?
1930 "Amaurotic family idiocy (Tay-Sachs disease) clinical report of a case." Journal of Nervous and Mental Disease 71: 268-70.
The remaining LSDs in which LAMP-1 was not increased (Krabbe disease, MLD, and Tay-Sachs disease) had significant numbers of patients (44-71%) with increases in saposin concentrations (Table 2).
But we were willing to accept and love the child, no matter what." Eight months after implantation, Renee gave birth to a daughter, Brittany, and the Abshires became the parents of the first-ever baby born with the help of pre-implantation diagnosis for Tay-Sachs disease.
See also: Ataxia, Neurometabolic Disorders, Tay-Sachs Disease
Layal was admitted to hospital in October 2014 with acute asthma but quickly her condition deteriorated which was when doctors discovered she had Tay-Sachs disease.
Screening during pregnancy to determine if one or both parents are carriers of genetic disorders historically has involved testing for a limited number of conditions, such as cystic fibrosis, hemoglobinopathies, and Tay-Sachs disease. Patients usually are offered testing for 1 or 2 disorders, with test choices primarily based on patient race and ethnicity.
GM2 gangliosidoses including Tay-Sachs disease [TSD, Online Mendelian Inheritance in Man (OMIM) 272800], Sandhoff disease (SD, OMIM 268800) and GM2 activator protein deficiency (GM2; OMIM 272750) are rare lysosomal storage disorders of the sphingolipid metabolism due to an autosomal recessive inheritance.
As an example of the potential of that concept, she discusses the push within the Jewish community for prospective parents to test for Tay-Sachs disease. But, Rochman asks, wouldn't it be better for everyone to know ahead of time, just in case?
Kaplan, "Tay-Sachs disease screening and diagnosis: evolving technologies," DNA and Cell Biology, vol.
Ashkenazi Jews, for example, are most likely to be carriers of the mutated HEXA gene linked to (http://www.nhs.uk/Conditions/Tay-Sachs-disease/Pages/Introduction.aspx) Tay-Sachs disease , a fatal genetic disorder.
Non-invasive prenatal testing (NIPT) test can detect birth defects such as neural tube defects, Down syndrome, chromosome abnormalities, genetic disorders and other conditions, such as spina bifida, cleft palate, Tay-Sachs disease, sickle cell anemia, thalassemia, cystic fibrosis, Muscular dystrophy, and fragile X syndrome.
It is not about questioning God's purposes in the context of Tay-Sachs Disease, as the title might suggest.