Eventually, loss of motor skills will be accompanied by loss of vision and hearing, seizures, paralysis and loss of intellectual abilities. Sufferers also may develop something called cherry-red spot in the back of the eye. As the disease advances, symptoms worsen and other organs are affected, eventually causing the child to die very early, usually before age 5. Disabilities in those who have Tay-Sachs symptoms usually become severe by age 2, with the child becoming completely disabled and unable to communicate or help him or herself.

There are also forms of the disease that can appear in adolescence and early adulthood, but they are usually milder than the infant form and are extremely rare. These include loss of muscle coordination, weakness, and problems with movement and speech.

The afflicted may also suffer from mental illness. The symptoms vary widely among individuals within the adolescent and adult-onset forms but usually start to manifest before age 5 and result in death by age 15. A form called late-onset Tay-Sachs may develop in which there is muscle weakness and slurred speech, but mental abilities remain normal.

How Tay-Sachs Is Acquired

Children are believed to inherit the gene from both parents, but not everyone who carries the gene acquires the disease, so it is a serious issue to confront. If both parents are carriers of the Tay-Sachs gene, then there is a 50 percent chance that offspring will carry the gene but be unaffected.

There is a 25 percent chance they will not carry the gene, and a 25 percent chance that the child will get the disease. A genetic counselor can explain in detail the chances of acquisition after obtaining the results of the blood test and going over the family history.