Tay-Sachs disease is a genetic disorder that causes an early breakdown of the nervous system. Most people born with this disease do not survive past their third birthday.
Tay-Sachs disease is caused by an enzyme defect. An important enzyme, hexosaminidase A, is not completely formed. Because of this enzyme defect, the body cannot break down a protein that is normally found in cells of the body. When this happens, the protein accumulates in the nerve cells. Then, the nerve cells swell up and degenerate, causing a breakdown of the nervous system.
A defective gene causes the enzyme defect that leads to Tay-Sachs disease. The gene is autosomal recessive in character. Autosomal means that the gene is on one of the 22 pairs of non-sex chromosomes. Recessive means that there must be two copies of the gene for the disease to exist.
Tay-Sachs disease is most common among Jews of Eastern European origin, specifically Ashkenazi Jews. Among this group, the carrier frequency is 1 in 30. Among non-Jews the carrier frequency is 1 in 300.