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Tay-Sachs disease is a rare genetic disorder that progressively destroys nerve cells (neurons) in the brain and spinal cord.
The most common severe type, known as Infantile Tay–Sachs disease, becomes apparent around three to six months of age with the baby losing the ability to turn over, sit, or crawl. They also develop an exaggerated startle reaction to loud noises. An eye abnormality called a cherry-red spot, which can be identified with an eye examination, is characteristic of this disorder. This is then followed by seizures, hearing loss, intellectual disability and paralysis (inability to move). Death usually occurs in early childhood.
There is no treatment or cure for Tay-Sachs disease, nor is there any way to prevent or reduce the progression of this disorder.
Tay-Sachs disease occurs when the body lacks hexosaminidase A (HEXA). This is a protein that helps break down a group of chemicals found in nerve tissue called gangliosides, a fatty substance. Without this protein, gangliosides, particularly ganglioside GM2, build up to toxic levels in cells, often nerve cells in the brain.
Tay-Sachs disease is caused by a defective gene on chromosome 15. When both parents carry the defective Tay-Sachs gene, a child has a 25% chance of developing the disease. The child must receive two copies of the defective gene, one from each parent, in order to become sick. If only one parent passes the defective gene to the child, the child is called a carrier. They will not be sick, but may pass the disease to their own children.
Anyone can be a carrier of Tay-Sachs. But, the disease is most common among the Ashkenazi Jewish population. One in every 27 members of the population carries the Tay-Sachs gene.
Tay-Sachs disease is very rare in the general population. (Only 1 in 6400 babies.)
This condition is inherited in an autosomal recessive pattern, which means copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.
Waren Tay and Bernard Sachs, two physicians, described the disease's progression and provided differential diagnostic criteria to distinguish it from other neurological disorders with similar symptoms.
Both Tay and Sachs reported their first cases among Ashkenazi Jewish families. Tay reported his observations in 1881 in the first volume of the proceedings of the British Ophthalmological Society, of which he was a founding member. By 1884, he had seen three cases in a single family. Years later, Bernard Sachs, an American neurologist, reported similar findings when he reported a case of "arrested cerebral development" to other New York Neurological Society members.
Sachs, who recognized that the disease had a familial basis, proposed that the disease should be called amaurotic familial idiocy. However, its genetic basis was still poorly understood. Although Gregor Mendel had published his article on the genetics of peas in 1865, Mendel's paper was largely forgotten for more than a generation – not rediscovered by other scientists until 1899. Thus, the Mendelian model for explaining Tay–Sachs was unavailable to scientists and doctors of the time.
Here are just a few examples: