Tay-Sachs Disease

What Is It?

Tay-Sachs disease is an inherited disease caused by an abnormal gene. People with this abnormal gene lack an important enzyme called hexosaminidase A (HEXA) that helps to break down a fatty material called ganglioside GM2. This material builds up in the brain, and eventually damages nerve cells and causes neurological problems.

Infants usually begin to show signs of the disease between 3 and 6 months of age. Children with Tay-Sachs disease can become deaf, blind and paralyzed, and usually die by the age of 5.

Tay-Sachs disease is an autosomal recessive inherited disorder, meaning a child inherits one copy of the abnormal gene from each parent. The parents do not actually have the disease, but carry the Tay-Sachs gene and pass it on to the baby. If both parents have the abnormal Tay-Sachs gene, there is a one-in-four chance that the child will inherit the gene from both of them and have Tay-Sachs disease.

Tay-Sachs disease is most common in Ashkenazi Jews. About one in 30 people with this ancestry carry a copy of the gene. Some non-Jewish groups also have a higher chance of carrying the disease. They include people whose ancestors were French-Canadian, from the Louisiana bayou, or from Amish populations in Pennsylvania.

Three types of related conditions often are included in the definition of Tay-Sachs disease because they affect the same gene.

• A juvenile form usually appears between ages 2 and 5. The symptoms resemble those of classic Tay-Sachs disease, and death usually occurs by age 15.
• A chronic form usually appears by age 5. Symptoms resemble the classic form, but are milder, with muscle weakness, slurred speech, tremors and, sometimes, mental illness.
• An adult form, called late-onset Tay-Sachs, or LOTS, resembles the chronic form, but first appears much later in life, between the teens and the 30s.

Other names for Tay-Sachs disease include Tay-Sachs sphingolipidosis; infantile ganglioside lipidosis; cerebromacular degeneration; GM2 gangliosidosis, Type 1; and amaurotic familial infantile idiocy.

Symptoms

Early signs and symptoms of Tay-Sachs disease can include:

• Loss of muscle tone
• Exaggerated response to sudden noises
• Lack of energy
• Loss of motor skills, such as the ability to roll over, crawl, reach for things or sit up

In its advanced form, the disease causes a gradual loss of vision, deafness, seizures, gradual paralysis and dementia. Red spots may appear on the retina.

Diagnosis