KidsHealth.org Mon May 16, 8:00 PM ET
A healthy baby is able to develop vision, movement, hearing, and other vital functions, in part, because enzymes clear out fatty protein and other unwanted material that can interfere with growth.
But a baby with Tay-Sachs disease is born without one of those important enzymes, called Hexosaminidase A (Hex A). So, as those fatty proteins build up in the brain, they hurt the baby’s sight, hearing, movement, and mental development.
A child can only get Tay-Sachs by inheriting it. The genetic trait is relatively common among certain ethnic groups, such as Ashkenazi Jews. Because the disease can be detected before a child is born, couples in those ethnic groups who are thinking of having children may want to get a blood test to find out whether their child would be likely to have the disease.
Who Is at Risk for Tay-Sachs?
Each year, about 16 cases of Tay-Sachs are diagnosed in the United States. Although Ashkenazi Jews (Jews of central and eastern European descent) are at the highest risk for the disease, it is now also prevalent in non-Jewish populations, including Cajuns in Louisiana and French Canadians who live near the St. Lawrence River.
Some people carry the genetic mutation that causes Tay-Sachs, but do not develop the full-blown disease. Among Ashkenazi Jews, one in 27 people are carriers. In the general population, one in 250 people are carriers.
A child can only have Tay-Sachs disease if both parents are carriers of the gene. When two carriers have a child together, there’s a: