Tay-Sachs disease

Page last reviewed: 13/07/2011

Tay-Sachs disease is a rare and usually fatal genetic disorder that causes progressive damage to the nervous system.

In the most common form of the condition, symptoms usually begin at around five months of age, when a previously normal child's development begins to slow and they gradually lose their ability to move. Other symptoms can include muscle stiffness and fits. Eventually, the child will become blind and die prematurely, usually before the age of four.

Other rarer forms of Tay-Sachs disease can begin later in childhood. The severity of these types varies, but they are usually milder than the disease seen in young children.

Read more about the symptoms of Tay-Sachs disease.

There is currently no cure for Tay-Sachs disease, so treatment involves making the child feel as comfortable as possible by treating the associated symptoms.

Read more about treating Tay-Sachs disease.

What causes Tay-Sachs disease?

Tay-Sachs disease is caused by a genetic mutation. This happens when the instructions that are found in all living cells become "scrambled" in some way, causing one or more processes of the body not to work properly.

In Tay-Sachs disease, a genetic mutation known as the HEXA mutation results in the body not producing an enzyme called Hexosaminidase-A (Hex-A). Without this enzyme, a fatty substance called ganglioside builds up in the cells of the nervous system, causing them to stop working normally, eventually killing them.

Tay-Sachs disease is a type of autosomal recessive inheritance disorder. This means that the child inherits a faulty gene from both parents. Both parents have to be carriers of the HEXA mutation to be at risk of having a child with Tay-Sachs disease. If both parents are carriers, their child will have a 25% chance of developing the condition.

Read more about the causes of Tay-Sachs disease.

Screening

Screening for Tay-Sachs disease is recommended for people in high-risk groups. This includes people of Ashkenazi Jewish descent and anyone with a history of the condition in their family.

Screening can take place at two points, either before or after a baby is conceived. These screening methods are described as:

  • preconception screening - where potential parents are able to check whether they carry the HEXA mutation before starting a family
  • antenatal screening - where a foetus is checked to see whether two copies of the HEXA mutation have been inherited, which would cause Tay-Sachs disease to develop

Read more about preventing Tay-Sachs disease.

Who is affected by Tay-Sachs disease?

Tay-Sachs disease is rare. In England, it occurs in only 1 in every 360,000 births, which is the equivalent of it occurring once every five years in Ireland. As a result, most cases now occur in people who are not of Ashkenazi Jewish descent. Both males and females are equally affected by the condition. 

Gene
Genes contain information that you inherit from your parents, such as eye colour. They are carried by chromosomes.
Genetic disorder
A genetic disorder is a disorder caused by a fault in the genes. It is usually hereditary (runs in the family).
Spinal cord
The spinal cord is a column of nervous tissue located in the spinal column. It sends messages between the brain and the rest of the body.

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Ashkenazi Jews

It is estimated that around 1 in 30 Ashkenazi Jewish people are carriers of the HEXA gene, and without screening it is estimated that Tay-Sachs disease would develop in around 1 in every 2,500 babies of Ashkenazi Jewish parents.

As well as Tay-Sachs disease, people of Ashkenazi Jewish descent are also more likely to develop other genetic conditions such as:

  • Crohn’s disease  a digestive condition that cause symptoms such as diarrhoea and abdominal pain
  • cystic fibrosis  a condition where the lungs and digestive system become "clogged up" with thick, sticky mucus

Page last reviewed: 13/07/2011

A baby with Tay-Sachs disease will develop normally until they are around three to six months old. The average age that symptoms start is five months.

The first noticeable symptom is usually that your baby is excessively surprised and startled by noises, such as people clapping their hands or a telephone ringing. You may also notice that a red spot appears near the centre of each of their eyes.

It is likely that your baby will be much slower in reaching developmental milestones, such as gripping objects and learning to crawl. Additional symptoms usually develop after about eight months of age and quickly become more severe. They include:

  • increasing muscle weakness that progresses to paralysis (inability to move body parts)
  • increasing loss of vision
  • loss of hearing 
  • difficulties swallowing (dysphagia)
  • muscle stiffness (spasticity)
  • lack of interest in the world around them
  • repeated fits

Due to the increasing damage to the nervous system, children with Tay-Sachs disease become increasingly vulnerable to infection, particularly lung infections. Many children with the condition die from a complication of an infection.

If your child has Tay-Sachs disease, it is highly unlikely that they will live longer than four years.

Rarer forms of Tay-Sachs disease

There are two much rarer forms of Tay-Sachs disease:

  • juvenile form
  • late-onset form

Juvenile form

In the juvenile form, the symptoms do not usually begin until a child is 3 to 10 years old.

Initially, the child will have problems with speech and motor skills, such as balance, walking and holding objects. Some children may also develop problems with vision.

As the condition progresses, the child will have repeated fits and experience an increasing loss of mental abilities such as memory, thinking and understanding. This is known as dementia. Dementia is usually associated with ageing, but it can affect people of all ages, although it is rare in children.

Children with the juvenile form of Tay-Sachs disease will usually die at around 16 years of age due to a complication of an infection.

Late-onset form

As the name suggests, the symptoms of late-onset Tay-Sachs disease develop later in life, usually during the teenage years.

Symptoms include:

  • slurred speech
  • loss of balance
  • loss of co-ordination
  • uncontrollable shaking of the hands
  • muscle cramps and twitching
  • muscle weakness, particularly the muscles that support the trunk which can make tasks like sitting up and getting out of bed difficult

Around a third of people with late-onset Tay-Sachs disease will also develop psychosis. Psychosis is a mental health condition where a person is unable to tell the difference between the real world and their imagination. They may see or hear things that aren't there (hallucinations) or believe things that aren't true (delusions).

Life expectancy is usually unaffected in cases of late-onset Tay-Sachs disease.

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Page last reviewed: 13/07/2011

Tay-Sachs disease is caused by a genetic mutation called the HEXA mutation.

As a result of the mutation, the human body does not produce an enzyme called Hexosaminidase-A (Hex-A). Enzymes are proteins that the body uses to trigger chemical reactions.

The Hex-A enzyme plays a vital role in helping to remove a fatty substance called ganglioside, which can build up inside nerve cells. Without the Hex-A enzyme, ganglioside will build up inside the nerve cells and the cells will gradually stop functioning. This can have a catastrophic effect on many of the systems and functions of the body including:

  • vision and hearing
  • speech
  • physical movement
  • the ability to think

Autosomal recessive mutation

All the genes in your body come in pairs. You receive one half of the pair from your mother and the other half from your father.

The HEXA mutation that causes Tay-Sachs disease is an autosomal recessive mutation. This means that a child receives two copies of the mutated gene, one from their mother and one from their father.

If you only receive one copy of the mutated gene from one of your parents, you will not develop Tay-Sachs disease. However, you will be a carrier of the mutated gene.   

If you are a carrier of the HEXA mutation and you have a baby with a partner who is also a carrier of the HEXA mutation, there is:

  • a 25% chance that the baby will receive a pair of normal genes and will not develop the condition
  • a 25% chance that the baby will receive a pair of mutated genes and will develop Tay-Sachs disease
  • a 50% chance that the baby will receive one normal gene and one mutated gene, and will become a carrier of the HEXA mutation but will not develop any symptoms

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Page last reviewed: 13/07/2011

A diagnosis of Tay-Sachs disease would be strongly suspected if a young baby develops the two symptoms that are most closely associated with the condition.

These symptoms are:

  • an exaggerated response to sudden noises 
  • red spots inside the eyes

Blood tests can also be carried out to check whether the body is producing the Hexosaminidase-A (Hex-A) enzyme. See causes of Tay-Sachs disease for more information.

If there is any doubt about the diagnosis, it can usually be confirmed by taking a blood sample and extracting DNA from it to check for the HEXA mutation.

Receiving the diagnosis

Being told that your baby has a fatal and incurable condition is a devastating experience, and it's likely that any parent in that position will experience profound feelings of grief, bereavement and, sometimes, guilt.

The National Tay-Sachs & Allied Diseases Association is an American foundation for people who are affected by Tay-Sachs disease. Their website has information about ways of treating the symptoms as well as useful advice about coping with the emotional impact of the condition.

The UK-based charity Genetic Alliance UK also provides information and services for people who have been affected by genetic conditions such as Tay-Sachs disease.

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Page last reviewed: 13/07/2011

As there is currently no cure for Tay-Sachs disease, the aim of treatment is to make a child living with the condition as comfortable as possible.

The main aims of treatment are to:

  • prevent problems with the lungs and airways
  • help the child's swallowing problems (dysphagia)
  • use medication to control, or at least partially relieve, symptoms such as fits and muscle stiffness

Your child's care plan

Due to the rareness of Tay-Sachs disease, it's likely that you will be referred to a specialist centre that has experience in treating children with complex health needs.

Children with Tay-Sachs disease can have complex needs. Therefore, they will need to be treated by a team of different specialists working together. These types of teams are called multi-disciplinary teams (MDTs).

After the initial diagnosis, you and your child will probably need to spend some time at the specialist centre so that a detailed treatment plan can be drawn up.

Once your child's symptoms stabilise, your MDT should be able to speak to your GP or your local primary care trust so that any necessary treatment can be given where you live. This will mean that you and your child will only have to visit the centre occasionally.

The lungs and airways

Children with Tay-Sachs disease are more vulnerable to developing problems with their lungs and airways. This is because:

  • Food or liquid can fall into the lungs and trigger an infection. This type of infection is called aspiration pneumonia.
  • They have increasing muscle weakness which can result in poor cough reflexes and in their lungs and airways becoming congested with mucus.
  • Children with Tay-Sachs disease are prone to drooling and the excessive production of saliva can further disrupt breathing.

These are described in more detail below.

Aspiration pneumonia

Aspiration pneumonia can be very difficult to prevent in children with Tay-Sachs disease, even if the care they receive from their parents and health professionals is of the highest standards.

Antibiotics are the most common form of treatment for aspiration pneumonia. Depending on the severity of the symptoms, the child may be given antibiotic tablets or injections. In particularly severe cases where airways become inflamed and swollen, a tube may be required to help keep the airways open.

Congestion

Congestion of the lungs by mucus can usually be treated with a type of therapy known as physical therapy of the chest, or chest PT for short.

Chest PT involves several techniques, such as using your hands to pat your child's chest to help encourage their cough reflex. Only attempt chest PT if you have been properly trained by a qualified healthcare professional. Performing the technique incorrectly could damage your child's lungs.

Drooling and saliva

Two medications that are fairly effective in reducing the production of saliva and controlling the symptoms of drooling are:

  • hyoscine skin patches - originally designed to treat motion sickness, these patches are similar to those worn by people trying to give up smoking and have the useful side effect of causing dryness of the mouth
  • trihexyphenidyl - this medication is available in syrup form and also causes dryness of the mouth

Feeding young children

Feeding young babies with initial symptoms of Tay-Sachs disease can be difficult because they often lack a suck reflex. This means they have problems latching on to a nipple or the teat of a bottle. The following advice may help.

  • Hold your baby on your lap so that you have both hands free. You can then use one hand to hold the nipple or bottle teat and the other hand to help with closing the baby's lips around it.
  • Before introducing the teat or nipple into the baby's mouth, it is a good idea to stimulate their mouth by gently tapping or stroking their tongue, lips and cheeks.
  • If breastfeeding, it may be a good idea to place a bottle teat over your nipple. This will allow you to help your baby suck by placing pressure on the teat.
  • You can help your baby's suck reflex by placing your finger on the middle of their cheek and gently stroking towards their lips.
  • Once your baby begins to suck, gently pull back the nipple or teat to encourage them to hold on.
  • If your baby is having difficulty swallowing, stroke them under their chin, down to the top of their breastbone in a one-way downward movement.

Several specialist bottles are available to make feeding easier. They are designed for children with a cleft lip or palate (a type of birth defect that affects the mouth), but are also useful for babies with Tay-Sachs disease.

As your child gets older and moves onto solid food, they may require a feeding tube. There are two main types of feeding tube:

  • a tube that is passed down the nose and into the stomach (nasogastric tube)
  • a tube that is surgically implanted directly into the stomach (percutaneous endoscopic gastrostomy or PEG tube)

PEG tubes are usually recommended for children with Tay-Sachs disease because they are designed for long-term use.

Medication

Medication such as gabapentin and lamotrigine can be useful in preventing seizures, though this can become more difficult as the condition progresses and higher doses may be required.

Problems with muscles, such as muscle stiffness and cramping, can be relieved using medications designed to relax the muscles (muscle relaxants), such as diazepam.

 

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Page last reviewed: 13/07/2011

Screening

Screening for the HEXA mutation that causes Tay-Sachs disease is recommended if you are planning to start a family and you are in a high-risk group for developing Tay-Sachs disease.

In these islands, two main groups of people are thought to have a high-risk of developing the condition:

  • people of Ashkenazi Jewish descent - this applies to most people of Jewish descent in England
  • people with a known history of Tay-Sachs disease in their family

Screening involves testing both yourself and your partner for the HEXA mutation. If you both test positive, you have a 25% chance of conceiving a baby who develops Tay-Sachs disease. This can be confirmed by testing the unborn foetus at an early stage of the pregnancy.

Content provided by NHS Choices www.nhs.uk and adapted for Ireland by the Health A-Z.

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