Tay-Sachs Disease: Symptoms, Causes, Treatment And Prevention
Tay-Sachs disease is a rare medical condition which, although rare in the majority of the population, it seems that there are ethnic groups in which it has a high prevalence.
It is a genetic disease that affects the nervous system, causing lipids present in nerve cells to accumulate and end up damaging them.
Let’s discover what causes this disease, what its main symptoms are, how it is treated and how it can be diagnosed, as well as see in which populations it is most likely to find people with Tay-Sachs disease.
Tay-Sachs disease, also called GM2 gangliosidosis and lysosomal storage disease, is a life-threatening medical, neurodegenerative and genetic condition that often affects children at an early age Its form of transmission is from parents to children, that is, it is hereditary, specifically autosomal recessive. In fact, it has been seen that certain populations, such as Ashkenazi Jews and the Amish community, are prone to having cases of this disease.
It is a rare disease, which It occurs when the body cannot break down fatty substances, causing them to accumulate at toxic levels in the nervous system of the affected person, causing this system to progressively degenerate. The child gradually loses muscle control, suffering visual loss and paralysis until he finally dies.
Causes
Tay-Sachs disease is caused by a defective gene on chromosome 15 and is inherited in an autosomal and recessive manner. If both parents have a defective copy of the gene, there will be a 25% chance that their child will have the disease.
To manifest it, you must have inherited both copies of the defective gene , one coming from the father and the other coming from the mother. If you have only inherited one defective chromosome, you will not manifest the disease, but you will be a carrier.
This gene in non-pathological conditions codes for the alpha subunit of the enzyme hexosaminidase A or Hex-A, a protein that helps break down gangliosides, especially GM2. These gangliosides are a group of lipids found in nervous tissue.
Hex-A is normally found in the lysosomes of nerve cells , organelles that degrade large molecules to recycle them. Without the enzyme, gangliosides accumulate in neurons and damage them little by little.
It should be said that although people who have two copies of the defective gene are those who will manifest Tay-Sachs disease, without being able to synthesize hexosaminidase A, people who are carriers may have altered levels of this enzyme. They do produce it and therefore do not suffer symptoms, but they only synthesize half the normal amount of Hex-A.
Risk factor’s
Anyone can be a carrier of the defective gene that causes Tay-Sachs disease. However, it has been seen that There are certain populations that have more cases of this disease, because the defective gene is more prevalent in their ethnic groups
A case of this is the Ashkenazi Jewish population, in which one in every 27 members is a carrier of the gene that causes this disease. Among the populations where the defective gene is most prevalent we have:
Symptoms
There are three types of Tay-Sachs disease: childhood, juvenile and adult These forms vary in their appearance and symptomatology, however, it should be said that the juvenile and adult forms are extremely rare.
The most common is the infantile form, which involves very early mortality. The disease already causes damage when the fetus is still in the womb, and symptoms are generally visible when the baby is between 3 and 6 months old. In most cases, the child dies when he or she is 4 or 5 years old.
Among the symptoms that can be found in this disease we have:
Cases of this disease have been documented in adults, but it is very rare and has a very late start. It is not detectable until the age of 20 or 30 and, in general, its symptoms are less severe than in the childhood form, although it can lead to a great degree of disability in the patient.
Diagnosis
To confirm that it is a case of Tay-Sachs, the first thing to do is find out if there is a history of the disease in both parents in addition to finding out if they are part of one of the four ethnic groups with the highest frequency of the defective gene.
In addition to this, they are made tests of the level of enzymes in the baby’s blood and body tissue , to check hexosaminidase levels. An eye exam will also be performed to see if cherry red spots appear on the macula.
Treatment
There is currently no effective treatment to cure Tay-Sachs disease. Unfortunately, if this disease is diagnosed in a baby, it is expected that he or she will not live more than 5 years. Nevertheless, The use of ganglioside synthesis inhibitors and Hex-A enzyme replacement therapies has been investigated as potential treatments for this rare disease.
It has also been investigated in gene therapies. One of them would consist of, through genetic engineering, including in the DNA of the child with the defective gene a gene that solves the abnormal synthesis of the Hex-A enzyme. It is still a very experimental and highly controversial technology, in addition to being quite expensive.
The surest way to guarantee that you will not have Tay-Sachs disease is for two people who are carriers of the defective gene not to have children together. Genetic tests can detect whether or not you are a carrier in addition to being aware if there have been cases of children dying at an early age in the family.
If both members of the couple have the defective gene, they should be aware that they have a 25% chance of having a child with the disease.
If the mother is already pregnant, the amniotic fluid can be analyzed to determine whether or not the baby will have the disease. If she has inherited two defective copies of the gene, it is confirmed that she could manifest the disease, and it is the parents’ decision to terminate the pregnancy.
In fertilization therapies there is the possibility of performing a preimplantation genetic diagnosis to make sure the baby will not get the disease. It consists of fertilizing the eggs extracted from the mother and, once the embryos are very primitive, selecting those that do not have any copy of the defective gene.
This same method has been used for other diseases of genetic origin, such as cystic fibrosis, sickle cell anemia and Huntington’s disease, but it must be said that it is a very expensive method that requires very invasive medical technology.
