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Understanding Tay-Sachs Disease

Tay-Sachs disease is the destruction of the nervous system commonly happens to children and infants / Photo by Getty Images

 

Tay-Sachs disease is a fatal genetic disorder, which is commonly happening in children and infants. This disease results in the progressive destruction of the nervous system. Tay-Sachs is caused by the absence of a vital enzyme called hexosaminidase-A. Genetics Home Reference explained on their website that infants who have this disease also experience the loss of control on their basic motor skills which makes it hard for them to move like a normal child.

Aside from their motor skills, children with Tay-Sachs disease also suffers from frequent seizures, hearing and vision loss, learning disability, and paralysis. Most affected infants have nerve damage starting in utero, with symptoms appearing from age 3 to 6 months, in most cases. Progression is rapid, and the child will typically pass away by 4 or 5 years old. This disease is commonly inherited from a person’s parents in an autosomal recessive manner. The mutation results in problems with an enzyme called beta-hexosaminidase A which results in the buildup of the molecule GM2 ganglioside within cells, leading to toxicity.

A baby with Tay-Sachs disease appears normal until about six months of age when its development eventually slows down. By two years of age, most children experience recurrent seizures and diminishing mental function. The infant gradually regresses and is eventually unable to crawl, turn over, sit or reach out. Eventually, the child becomes blind, cognitively impaired, paralyzed and non-responsive. Mutations in the HEXA gene disrupt the activity of beta-hexosaminidase A, which prevents the enzyme from breaking down GM2 ganglioside. As a result, this substance accumulates to toxic levels, particularly in neurons in the brain and spinal cord. Progressive damage caused by the buildup of GM2 ganglioside leads to the destruction of these neurons, which causes the signs and symptoms seen in Tay-Sachs disease.

Inheriting Tay-Sachs Disease

In a web post by Cats Foundation, they mentioned that 1 in 300 people could be a carrier of the genes which could cause Tay-Sachs or Sandhoff disease. Apparently, there is still no cure available for this rare type of genetic disease and scientists and researchers are still on their way in finding a solution in which they could stop this disease from taking its toll from infants and children all over the world. It is known that this disease is inherited but studies also showed that the person’s family anthropological history also affects the onset of this disease.

Cri Genetics explained on their website that 1 in 4 of Ashkenazi Jewish people has shown certain genetic disorders including Tay-Sachs, anemia, and Canavan disease. The genetic isolation and limited marital options have resulted in their lineage to be susceptible to different inherited diseases. Screening for carriers of Tay-Sachs was started in the 1970s and has reduced the number of Ashkenazi Jews born with Tay-Sachs by 90 percent.

Likewise, Tay-Sachs results from mutations in the HEXA gene on chromosome 15, which encodes the alpha-subunit of beta-N-acetylhexosaminidase A, a lysosomal enzyme. By 2000, more than 100 different mutations had been identified in the human HEXA gene. These mutations have included single base insertions and deletions, splice phase mutations, missense mutations, and other more complex patterns. Each of these mutations alters the gene’s protein product, sometimes severely inhibiting its function. In recent years, population studies and pedigree analysis have shown how such mutations arise and spread within small founder populations.

 

Vision loss is one way how Tay-Sachs disease is affecting children and infants / Photo by Joel Claheiros via 123RF

 

Tay-Sach Disease Management

Although there is no cure or effective treatment for Tay-Sachs disease, a simple blood test can identify Tay-Sachs carriers. Blood samples can be analyzed by either enzyme assay or DNA studies. The enzyme assay is a biochemical test that measures the level of Hex-A in a person’s blood. Carriers have less Hex-A in their body fluid and cells than non-carriers. It can be performed using serum or leukocytes isolated from blood. The serum is most commonly used but leukocyte screening is recommended when the person is pregnant, taking birth control pills, or on any medications that affect hormones.

Parents could also try two tests in order to know whether if their baby has Tay-Sachs. Chorionic villus sampling is a test done between the 10th and 12th weeks of pregnancy. The doctor will put a needle into the pregnant mother’s belly or places a tube through the vagina into the cervix. Then the doctor will remove a small piece of tissue from the placenta, the organ that gives nutrients and oxygen to the baby while the tissue obtained will be tested to the laboratory.

On the other hand, Amniocentesis is a test done between 15th and 18th weeks of pregnancy. The doctor will use a thin needle to remove a sample of amniotic fluid. This fluid surrounds the baby inside the mother’s womb. Couples who are both carriers of the same disease will want to explore their many options for a healthy family. It is best to consult a genetic counselor who can explain the various choices that are applicable to the couple.

 

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