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Transcript of Tay Sachs
How to know ?
Why it mostly affects Jews ?
There is no definite answer why this disease mostly affects Ashkenazi Jews . But there are some strong theory's. First theory involves an infectious disease called tuberculosis. For some reason evidence shows that Tay Sachs provides some protection from TB and it may explain why Ashkenazi Jews have a high carrier disease. When World War 2 broke out TB spread across eastern European Jewish settlements. This was particularly dangerous because the Jews were forced to live in the ghettos, so they couldn't move out. However some healthy parents who had children with Tay Sachs disease did not contact TB, even though they were sometimes were repeatedly exposed to it. These parents must have been carriers of Tay Sachs in order to have children with this disease. Therefore being a carrier of Tay Sachs seems to provide some sort of protection against TB, however why it provides protection is still unknown.
What is Tay Sachs ?
Tay sachs is a disease of the central nervous system, its neurodegenerative disorder. This disease occurs when the body lacks hexosaminidase A. A protein that helps break down a chemical found in nerve tissue called ganglioside. Without this protein, gangliosides, particularly ganglioside GM2, builds up in cells, especially nerve cells in the brain. This disease is transmitted genetically. Tay Sachs disease is caused by a defective gene on chromosome 15. Tay sachs is commonly affected in infants, its a progressive disease that is mostly always fatal in children, it rarely occur in adults, causing less severe. The nerve damage usually begins while the baby is still in the womb. Symptoms usually appear when the child is 3-6 months old. The disease tends to get worse very quickly, and the child usually dies by age 4 or 5. There is no way to prevent this disorder. There is also no way to cure or any effective treatment.
A child can only get Tay Sachs by inheriting it. The genetic trait relatively common among certain ethnic groups, such as Ashkenazi Jews. When two carriers have a child together, there’s a :
50% chance that their child will be a carrier, but not have the disease
25% chance that their child will not be a carrier and not have the disease
25% chance that their child will have the disease
The genetic trait relatively common among certain ethnic groups, such as Ashkenazi Jews. Even though Ashkenazi Jews (Jews in central and eastern European descent) are at a high risk and now some non-jewish population are getting this disease including French-Canadians/Cajun heritage. Most people are carriers of this disease but don’t develop the full-blown disease. Among Ashkenazi Jews, 1 in 27 people are carriers, in the general population, 1 in 250 people are there.
History of Tay Sachs
The disease is named after the British ophthalmologist Warren Tay, who in 1881 first described a symptomatic red spot on the retina of the eye, and after the American neurologist Bernard Sachs of Mount Sinai Hospital, New York, who described in 1887 the cellular changes of Tay-Sachs disease prevalence in the Eastern European Ashkenazi Jewish population. They both reported their first case of Tay Sachs in Jewish families. Tay reported his observations in 1881 to the first of the proceeding of the British Ophthalmological Society, of which he was a founding member. By 1884 he had already seen three cases in a single family. Years later, Bernard Sachs, an american neurologist, reported similar cases. Sachs who recognized that the disease had a familial basis, proposed that the disease should be called amaurotic idiocy. However, it is a genetic basis was still poorly understood. Then in 1969, Shintaro Okada and John S. O’Brien showed that Tay-Sachs disease was caused by a defect and also proved that Tay Sachs patients could be diagnosed. During the early 1970s, researchers developed protocols for newborn testing,carrier screening, and prenatal diagnosis. By the end of 1979, researchers had identified three different forms of GM2, including Sandhoff disease and the AB different of GM2-gangliosidosis, accounting for negatives in carrier testing.
Genetic testing is generally done when one or both members of a couple are carriers of the disease. If a child may seem to have symptoms, a doctor can perform a physical examination and collect a family history. Tay Sachs can be detected before birth, about 16 cases of Tay Sachs are diagnosed in the United States. Enzyme analysis can be done on the child’s blood or tissue sample and eye exam may reveal a red spot on his or her macula knows as cherry-red spot. A cherry- red spot as seen in Tay Sachs disease. The fovea center appears bright red because it surrounded but milky halo. The fovea centralis, also known as the fovea (the term fovea comes from the Latin word, meaning pit or pitfall), is a part of the eye located in the retina, The Fovea is responsible for sharp vision, which is necessary in the human for activities where visual detail is of primary. Prenatal tests such as chorionic villus sampling (CVS) and amniocentesis, can diagnose Tay-Sachs .
Researchers are pursuing several approaches to finding
a cure. Scientists are exploring enzyme replacement therapy to provide the Hex-A that is lacking in babies with Tay-Sachs. Bone marrow transplantation has
been attempted also, but
to date has not been successful in reversing or slowing damage
to the central nervous system in babies with Tay-Sachs. Another avenue of research is gene therapy in which scientists transfer a normal gene into cells to replace an abnormal gene.
Symptoms usually occur when baby is around 3-6 months of age, then the baby starts to have muscle weakness, low muscle tone, an increased startle response and sudden contractions of large muscles when falling asleep, which is known as myoclonic jerks, between 6-10 months of age, a child will not meet motor expectations and may lose the ability to perform tasks (such as sitting) that he/she had already learned. Decreased eye movement and contact as well as attentiveness are also seen along with a specific change in the eye seen during exam called a cherry-red spot. After about 8-10 months of age, a baby will move less and become less responsive. Visions will be lost and many seizures will occur by a year of age. They typically have trouble swallowing and progress into an unresponsive vegetative state.