This condition, Tay-Sachs Disease, is due to the reduction of a key enzyme. This missing enzyme is hexosominidase and is commonly referred to as Hex A. When this enzyme is missing in lipids (fats), GMZ ganglioside accumulates in inert cells. Hex A is key and is needed to break up and regulate lipids. When GMZ builds up in the nerons, the functions of the nervous system are affected. This leads to mental retardation, damages in the nervous system, and results in death by age 5.
One unique statistic of this disease is that it is found predominantly (but not exclusively) among the Ashkenazi Jewish community. As we relate the areas of the Jewish population in the U.S. to that of Israel, we see the statistic leading to approximately 1 in 67,000 in the U.S. compared with 1 in 14,000 in the Israeli areas.
The statistical information tells us that there is about 5-15% residual activity in Late Onset
Tay-Sachs as it is relatively absent in the infantile form.
The most common symptoms that come along with this disease are: clumsiness, tremors, falls, abnormal behaviors, or mood alterations. The signs of late onset Tay-Sachs can be seen from the period of late adolescence and the mid-30's. However, this may vary. This is a rather difficult disease to detect simply due to the fact that it is slowly progressive.
More in-depth symptons are: proximal muscle weakness, muscle cramping, especially in the legs at night, muscle wasting, fasiculations (twitching of muscles), lack of coordination, unsteady gait, head tremors, dysarthria (slurred speech), and dystonal muscle contractions causing distortion of posture). Some symptons that are less common of Tay-Sachs are: sensory impairment, chorea (irregular involuntary movements), and seizures. Note that not all of these are present with every person living with Tay-Sachs. Many persons living with this disease undergo great frustration.
In the process of metabolism, the cells age quickly and then die. They must be disposed of and then accumulate in nerve cells along with the unbroken lipids. This slowly deteriorates the nervous system.
Two different genes make up Hex A. Alpha-subunit and beta-subunit are the two genes that make up this protein (enzyme). There is also a third protein to this enzyme, making it a very large molecule. For Tay-Sachs to occur, there must be a mutation in at least one of the parent's genetic make up on chromosome A15.
Infantile and late onset Tay-Sachs are both forms of autosomal recessive conditions. In order for a gene to be recessive, there must be a mutation in the DNA to prevent it from working properly. Two autosomal recessive carriers have a 25% (1-4) chance of having an affected child.
Late onset affected people have a 100% chance of passing an A-subunit gene with mutation to each of his or her offspring. This gives away to risks of the offspring inheritance of either infantile or late onset forms of this disease.
The Askenazi Jewish population is well known for being at high risk for this disease. This is based upon the information that 1 in 30 persons of Ashkenazi Jewish background is a carrier for this genetic disease. You can compare this with 1 in 300 persons of non-Jewish background. Central and Europeans are not the only culturally basis of high risk. So far cases of non-Jewish persons of French-Canadian ancestry (Cajun population in Louisiana) are becoming more and more at a higher risk. These two groups have approximately 100 times the rate of occurance than other ethnic groups.
To determine if you are a carrier, a simple way for going about this is to take a blood test. By doing so, the amount of Hex A is measured from your blood.
From blood tests genetic testing is also available. Sometimes genetic testing is recommended after unpleasant blood tests.
Tay-Sachs is often referred to as Juvenile, chronic, or adult-onset forms of Hex A deficiency. As we can see, the infantile form of Tay-Sachs often results in death by age 5. This is the classic and most severe of the various types. The adult-late set forms are more mild, but severe in many ways yet. Their symptoms also develop later in life.
There aren't currently any known treatments that will prevent Tay-Sachs, only medicines that make the person living with Tay-Sachs more comfortable. These are used to manage the symptoms. However, anticonvolutants are used for patients who experience seizures. Antidepressents are available for
those going through frustration and psychiatric problems. Gene therapy is being experimented with for future treatments.
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