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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 for Tay-Sachs disease is recommended for people in high-risk groups. In England, 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:
In such a circumstance, the parents would be able to make an informed decision about whether to continue with the pregnancy.
Read more about preventing Tay-Sachs disease.
Who is affected by Tay-Sachs disease?
Due to the success of the screening programmes described above, Tay-Sachs disease is rare in the UK. 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.
Before screening was introduced, Tay-Sachs disease was most common in people of Ashkenazi Jewish descent. Ashkenazi Jews are descendents of Jewish communities from Central and Eastern Europe. Most Jewish people in England are 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:
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:
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:
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.
As the name suggests, the symptoms of late-onset Tay-Sachs disease develop later in life, usually during the teenage years.
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.
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:
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 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:
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.
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:
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. These may include:
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 Health Board 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:
These are described in more detail below.
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 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:
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.
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. You can buy specialist feeding equipment from the Cleft Lip and Palate Association.
As your child gets older and moves onto solid food, they may require a feeding tube. There are two main types of feeding tube:
PEG tubes are usually recommended for children with Tay-Sachs disease because they are designed for long-term use.
See the A-Z topic about Dysphagia for more information and advice.
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.
A difficult decision
As your child gets older, it's highly likely that they will experience repeated lung infections, which will damage their lungs and prevent them from breathing. This is known as respiratory arrest.
Respiratory arrest can be treated, although often with a low chance of success. In such circumstances, you and your partner may decide that you do not wish your child to be treated and that you would prefer them to die peacefully in their sleep.
If this is the case, you will make what is known as a Do Not Attempt Resuscitation (DNAR) order. Once the order is made, it will be placed with your child’s medical records. However, it can be withdrawn at any time should you change your mind.
This is a very difficult decision and there are no right or wrong answers.
Some parents decide that even if treatment prolongs their child’s life by just a few days or months, it is still precious time that they get to spend with their child.
Other parents feel that attempting to resuscitate their child will just prolong the inevitable and that treatment should be withdrawn. Discuss the issue carefully with your partner, your family and your loved ones.
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 England, two main groups of people are thought to have a high-risk of developing the condition:
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. If the diagnosis is confirmed, you have the option of terminating the pregnancy.
Some people are unwilling to terminate a pregnancy because they have ethical or religious objections to the practice of abortion. In such circumstances, an alternative option to conceiving naturally would be to surgically remove a number of eggs from the woman's ovaries and fertilise them with the man’s sperm in a laboratory. This is known as in-vitro fertilisation (IVF).
The resulting embryos can be tested and only healthy embryos selected for implantation back in the womb. However, IVF is only available free of charge on the NHS for women with fertility problems, so you would need to pay for treatment if you chose this approach. A course of IVF carried out privately can cost up to £7,000, and there is no guarantee that it will be successful.
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