Tay-Sachs Disease

Tay-Sachs Disease

Overview

Tay-Sachs disease is a genetic condition that causes damage and, ultimately, the death of nerve cells (neurons) in your child’s brain and spinal cord. Symptoms like developmental delays, hearing and vision loss usually begin around 6 months of age.

It’s a progressive disease, meaning it gets worse over time. It leads to early death. There’s no cure, but treatment supports your child and keeps them comfortable.

What are the types of Tay-Sachs disease?

There are three types of Tay-Sachs disease. The type depends on when symptoms develop:

Classic infantile: This is the most common form of Tay-Sachs disease. Children develop symptoms around 6 months of age.

Juvenile: Children develop symptoms between the age of 5 and their teenage years. This form is very rare.

Late-onset: Symptoms can appear during the late teen years or early adulthood. They can also develop after a person reaches 30 years old. This type may not affect your life expectancy. It’s also very rare.

The type of Tay-Sachs disease passes in families. For example, if one child inherits the infantile form, other children in the family aren’t at risk of late-onset Tay-Sachs disease.

Symptoms

Symptoms of Tay-Sachs disease vary based on your child’s age. The disease progresses (gets worse) as your child grows. The most common sign of Tay-Sachs disease among children is missing developmental milestones for their age or losing skills they previously learned and mastered.

Classic infantile Tay-Sachs disease symptoms

Early symptoms (around 6 months) include:

Muscle weakness.

Difficulty turning over, sitting or crawling.

Easily startled by loud noises.

As the disease progresses (before 1 year of age), symptoms include:

Involuntary muscle twitching (myoclonic jerks).

Seizures.

Difficulty swallowing (dysphagia).

Vision loss.

Hearing loss.

Cherry-red spot on their eyes.

Respiratory infections.

Around 2 years old, the condition starts to take over completely. Your child may be in an unresponsive state. This means they don’t have much brain function. The age of death is usually between 2 and 4 years. Pneumonia is often the cause of death in infantile Tay-Sachs disease.

Juvenile Tay-Sachs disease symptoms

Children diagnosed with juvenile Tay-Sachs disease may experience the following symptoms after age 5:

Muscle weakness or loss of muscle control.

Frequent infections.

Difficulty with speech and language (talking).

Loss of previously learned skills.

Mood and behavioral changes.

Hearing and vision loss.

Seizures.

The condition usually progresses into the teenage years and leads to early death during this time.

Late-onset Tay-Sachs disease symptoms

Adults diagnosed with late-onset Tay-Sachs disease may experience the following symptoms:

Muscle weakness and spasms.

Loss of coordination (ataxia) or the ability to walk.

Difficulty with communication and swallowing.

Psychosis or the development of mental health conditions.

Late-onset types don’t usually affect a person’s life expectancy.

Causes

A genetic change (mutation) of the HEXA gene causes Tay-Sachs disease.

The HEXA gene gives your cells instructions to make an enzyme (hexosaminidase A) that breaks down toxic substances in your body. If this enzyme isn’t available to do its job, a fatty substance collects in your cells. This damages and, ultimately, destroys cells within your brain and spinal cord, leading to symptoms of Tay-Sachs disease.

Tay-Sachs disease is autosomal recessive. This means that two copies of the disease-causing genetic variant (change or mutation) to the HEXA gene need to be present for a Tay-Sachs disease diagnosis.

Each person has two copies of the HEXA gene. They get one from each of their biological parents.

Tay-Sachs disease happens when both parents have a mutated HEXA gene and pass it on to their children. As a result, neither copy of the baby’s HEXA gene works. Healthcare providers may refer to this condition as hexosaminidase A deficiency or hex A deficiency.

What does it mean to be a Tay-Sachs carrier?

A carrier is a person who has one working copy of the HEXA gene and one copy with a disease-causing variant. All humans inherit two copies of a gene, one from each biological parent to make a pair (one from the egg and one from the sperm). Carriers don’t have the condition or show symptoms, as their bodies can rely on the one working gene.

If two people who carry the genetic variant have a child, the child’s risk of developing the condition is as follows:

A 25% (1 in 4) chance that the child won’t inherit any variant HEXA genes. The child won’t have Tay-Sachs disease or be a carrier.

A 50% (1 in 2) chance that the child gets a variant gene from one parent. When this happens, the child will be a carrier but won’t have Tay-Sachs disease. As they’re a carrier, they may pass it on to their children.

A 25% (1 in 4) chance that the child gets a variant gene from both parents. In this case, the child has Tay-Sachs disease.

What are the risk factors for Tay-Sachs disease?

A child is more at risk of developing Tay-Sachs disease if both of their biological parents carry the genetic variant. Anyone can be a carrier of the genetic variant. The condition is more common among people of French-Canadian, Eastern European or Ashkenazi Jewish descent, where approximately 1 in 30 people carry the genetic variant.

What are the complications of Tay-Sachs disease?

Tay-Sachs disease causes early death among children. As the condition progresses, a child’s life expectancy decreases.

Diagnosis

A healthcare provider will diagnose Tay-Sachs disease after a blood test. To perform this test, a healthcare provider will remove a small sample of blood from your child’s body, either their heel or a vein in their arm. Their provider will measure the level of the enzyme hexosaminidase A in the blood sample. In a child with classic Tay-Sachs disease, this protein is mostly or completely missing. People diagnosed with other forms of the disease have low levels of this enzyme.

A provider may also do an eye exam to see if the child has the classic cherry-red spot in their eye.

Can Tay-Sachs be diagnosed during pregnancy?

Two specialized tests can diagnose Tay-Sachs disease during pregnancy:

Amniocentesis: Your healthcare provider will remove a sample of amniotic fluid (the fluid that surrounds a fetus in your uterus) to test it.

Chorionic villus sampling (CVS): Your healthcare provider will remove a small piece of tissue from the placenta to test it.

Both tests look for the enzyme hexosaminidase A. If there’s a below-average amount of this enzyme in the testing samples, your healthcare provider will diagnose the fetus with Tay-Sachs disease. In addition, they may perform a genetic test on these samples to identify a mutation in the HEXA gene, which causes the condition.

Treatment

Treatment for Tay-Sachs disease is supportive of your child’s symptoms. For example, your healthcare provider may prescribe medication to manage seizures. Other treatment measures include providing proper nutrition and hydration. Your child’s provider will make them as comfortable as possible.

In addition, your healthcare provider can help you and your family prepare for the loss of your child. They may recommend visiting a mental health professional or participating in a bereavement support group.

Treatment for late-onset Tay-Sachs disease

Treatment is available to help adults diagnosed with Tay-Sachs disease manage their symptoms, including:

Using assistive devices or mobility equipment (wheelchair) to help with independence and navigation.

Taking medication to manage mental health conditions or muscle spasms.

Speech therapy

Type of Doctor Department : A geneticist or pediatric neurologist