Tay-Sachs Disease

Tay-Sachs Disease is one of the most lethal genetic disorders The causes of Tay Sachs disease lie in a mutation in a single gene (monogenic genetic disease). The mutation that is responsible for the disease lies in the gene Hex A. This gene codes for the enzyme hexaminidase A and is found in the chromosome 15. The normal protein catalyzes the degradation of some fatty acids called gangliosides. Tay-Sachs Disease is a devastating and fatal illness caused by the lack of the enzyme hexosaminidase A (hex A). Tay-Sachs is of genetic origin. All who have Tay-Sachs get it from two parents who carry a recessive gene for the disease. These parents do not have Tay-Sachs because the disease in both its most common forms, infantile and juvenile Tay-Sachs result in mortality before children reach adulthoodThe most important ganglioside for Tay-Sachs is the Ganglioside GM2. This material is found in the nerve cells of the brain and especially in the cell membranes. In the case of Tay-Sachs Disease there is no enough activity of the enzyme and the gangliosides are accumulated with destructive results.

Answering to the question whether there is only one specific mutation that leads to Tay Sachs or not, we have to say that the mutations can happen to more than one site of the gene. A large number of HEXA mutations have been discovered, and new ones are still being reported. These mutations reach significant frequencies in several populations.

The cause of this deterioration is that hex A is not present to break down fatty tissues in the brain and nerves. Failure to metabolize these substances gradually results in the above symptoms and death, since the brain and nerves become more and more impaired by fatty tissues.

Juvenile Tay-Sachs causes affected children to develop symptoms around the age of three, though this can vary anywhere from two to five. The progression of the disease is very slow, taking up to 12 or 13 years for death to occur. Parents are heartbroken to see their children gradually lose previously acquired functions like talking and walking. Children with juvenile Tay-Sachs may still have the ability to understand, but speech if it exists will be slurred and unintelligible in late stages. Juvenile Tay-Sachs is also associated with more pain, as frequent muscle spasms and cramps occur.

On rare occasions, an adult will develop a hex A deficiency. His or her disease will be similar in course to those affected by juvenile Tay-Sachs. Predictors for this deficiency in adults are not well defined.

Tay-Sachs is often associated with European Jews. They do have the highest rate of being carriers of the gene responsible for Hex A deficiency. However, not only Jewish children get Tay-Sachs. The existence of the illness has been noticed in some French Canadians. As well, those whose have Cajun ancestry are more at risk.

One parent, who is a carrier, has a 50% chance of passing the carrying gene to children. When both parents are carriers each child has a 25% chance of being born with Tay-Sachs. Each child also will inherit a gene to carry the disease. Tay-Sachs can be diagnosed with chronic villus sampling during the early part of pregnancy. Many who then receive a positive diagnosis are faced with the difficult decision of whether to end a pregnancy and the life of their child at this point, since the outcome of the disease is likely fatal.