Tay-Sachs disease occurs when the body lacks hexosaminidase A, a protein that helps break down a chemical found in nerve tissue called gangliosides. Without this protein, gangliosides, particularly ganglioside GM2, build up in cells, especially nerve cells in the brain. Tay-Sachs disease is due to a defective gene on chromosome 15. When both parents carry the defective Tay-Sachs gene, a child has a 25 percent chance of developing the disease. The child must receive two copies of the defective gene in order to become sick. If only one parent passes the defective gene onto the child, the child is called a carrier. Anyone can be a carrier of Tay-Sachs. However, the rate of the disease is much higher among the Ashkenazi Jewish population. About 1 in every 27 members of the Ashkenazi Jewish population carry the Tay-Sachs gene. Tay-Sachs has been classified into infantile, juvenile, and adult forms, depending on the symptoms and when they first appear. Most people with Tay-Sachs have the infantile form. In this form, the nerve damage usually begins while the baby is still in the womb. Symptoms usually appear when the child is 3 - 6 months old. The disease tends to get worse very quickly, and the child usually dies by the age 4 or 5. Late-onset Tay-Sachs disease, which affects adults, is very rare. | 
General Pediatrics
