Tay-Sachs disease

Tay-Sachs disease is a rare and fatal disease most commonly diagnosed in children around 6 months of age.

This condition is incurable, but scientists have a good idea of what causes it, how it worsens, and how to use genetic testing to detect it early in pregnancy.

Researchers are working on advances in gene therapy or bone marrow transplantation, which they hope will allow treatment of Tay-Sachs syndrome in the future.

Symptoms of Tay-Sachs disease

A baby born with Tay-Sachs disease grows normally until the age of 3 to 6 months.

Around this time, parents may notice that their child's development begins to slow down and their muscles weaken. Over time, the disease causes more symptoms in children, including:

Loss of motor skills such as rolling, sitting and crawling
Very strong reaction to loud noises
Difficulty concentrating on objects or following them with your eyes
Cherry red spots, identifiable on eye examination, in the eyes

By the age of 2, most children with Tay-Sachs disease have more serious problems. They may include:

Swallowing and breathing issues that keep getting worse
Seizures
Loss of mental function, hearing, and sight
Paralysis

After 3 years, children with Tay-Sachs disease show little visible change, but their nervous systems continue to deteriorate, often leading to death before age 5.

Causes and risk factors for Tay-Sachs disease

Defects in a gene called HEXA cause Tay-Sachs disease. (You can think of genes as the "coding" your parents passed on to you. Genes are in your cells and determine the characteristics of your body, from eye color and blood type to your gender.)

Most people have two healthy versions of this HEXA gene, which instructs your body to make an enzyme (a type of protein) known as Hex-A. This enzyme prevents the accumulation of a fatty substance called GM2 ganglioside in the brain and spinal cord.

Some people have only one healthy copy of the gene and still make enough Hex-A protein to keep their brain and spinal cord healthy. But children born with Tay-Sachs disease have an altered copy of the gene from both parents, so they don't make Hex-A proteins. That's what makes them so sick.

Over time, GM2 ganglioside accumulates in their nervous system and begins to wreak havoc.

The disease is very rare. It only affects about 1 in 112,000 live births.

Anyone can carry the HEXA mutation, which means having only one defective copy of the HEXA gene.

If both parents are carriers of Tay-Sachs disease, there is a 25% chance that one of their children will become infected.

Diagnosis of Tay-Sachs disease

Pregnant women may be tested to see if their unborn child has a problem that causes Tay-Sachs syndrome. If the tests do not detect Hex-A proteins, the child has Tay-Sachs disease. If the tests detect Hex-A, the child does not have the disease.

These tests include:

Chorionic villus sampling. Your doctor takes a small sample of the placenta with a needle or small tube and analyzes it. They can do this between the 10th and 12th week of pregnancy.
Amniocentesis. The doctor uses a needle to take a sample of the amniotic fluid surrounding the baby and test it.

To diagnose Tay-Sachs syndrome in a child after birth:

Your doctor will ask you about your child's symptoms and your family history.
They'll do a blood test to check the Hex-A level.
The doctor will check the child's eyes. A cherry spot behind the eyes is a sign of Tay-Sachs disease. If this is the case, you may need to take your child to specialists such as a pediatric neurologist and ophthalmologist for further evaluation.

Treatment of Tay-Sachs disease

Some of the specialists, procedures, and programs you might consider include:

Speech therapists. They can provide ways to help your baby maintain the suck-swallow reflex and help you determine when it's time to consider tube feeding your baby.
Neurologists. These professionals can help you manage your child's seizures with medication.
Respiratory health. Specialists such as pediatricians and pulmonologists (doctors who treat lung and breathing problems) can advise parents on how to reduce their child's risk of a chest infection.
Therapeutic exercise of the chest. Tapping on the chest wall can help break up mucus in the lungs so the child can cough it up.
Feeding tubes. Your child may have trouble swallowing or breathing, including breathing food or liquid into the lungs while eating. You can insert the feeding tube through the baby's nose into the stomach each time. Or the doctor may insert a tube during surgery.
Play and stimulation. You can help your child interact with the world through music, smells and textures.
Massage. They can relax your child.
Palliative and hospice care. These programs help manage the quality of life of children with Tay-Sachs disease and their families.

Prevention of Tay-Sachs disease

You can get a blood test that looks at your genes or the Hex-A protein levels in your blood to determine if you are a Tay-Sachs carrier.

If two people who are planning to have children find out they are both carriers, a genetic counselor can help them consider options to reduce their chances of having a child with Tay-Sachs disease.

Late-onset Tay-Sachs disease

An even rarer type of Tay-Sachs syndrome is called "late onset" or "adult onset". This can be difficult to diagnose.

Like the infant version of the disease, Tay-Sachs disease, which begins later in life, is caused by changes in the HEXA gene. Symptoms can begin to appear at any age, from adolescence to adulthood.

Early symptoms often include clumsiness, balance problems, and muscle weakness in the legs. Patients may also have mental health problems.

This form of the disease affects each person differently. Late onset of Tay-Sachs syndrome does not always mean a shorter life expectancy.