What is Tay-Sachs disease?
Tay-Sachs disease is a rare, inherited disorder that causes progressive damage to the central nervous system, including the brain and spinal cord. This damage results in a loss of muscle control and intellectual disability.
Tay-Sachs disease is caused by a defect in the hexosaminidase A enzyme (HEXA). This enzyme helps break down the fatty substance GM2 ganglioside in neurons. Without enough HEXA, GM2 ganglioside builds up and damages these cells. Eventually, this leads to brain cell death and other complications that affect many organ systems.
The symptoms of Tay-Sachs disease typically appear around 6 months of age and progress rapidly over several years until affected children become blind, deaf and unable to move or swallow on their own. Most die by age 4 or 5 from pneumonia or other complications related to their illness.
Who is at risk for Tay-Sachs?
Tay-Sachs disease affects people of all races and ethnic groups around the world. But it’s more common among people of Eastern European (Ashkenazi) Jewish descent than in others. In this group, there’s a 1 in 27 chance of having two copies of the defective gene — one from each parent — which increases their risk of having a baby with Tay-Sachs disease.
Tay-Sachs disease occurs when both parents are carriers for the genetic defect that causes this disorder. The risk of having a child with Tay-Sachs disease increases as more carriers appear in a family line. If both parents are carriers, each pregnancy has a 25 percent chance of resulting in a child with the disease; if only one parent is a carrier, each pregnancy has a 50 percent chance of resulting in a child with the disease; and if neither parent is a carrier, no children will be affected by Tay-Sachs disease.
How common is Tay-Sachs disease?
Family history of the disorder. If you have a family member with Tay-Sachs disease, you have a higher chance of developing it yourself than people who don’t have such a family history. You are also more likely to develop the disorder if your family has a history of another genetic disorder called Niemann-Pick disease type A or B (NPA or NPD).
Race or ethnicity. Tay-Sachs disease occurs more frequently among people of Eastern European Ashkenazi Jewish descent and Northern Europeans than among other ethnic groups.
What are the forms of Tay-Sachs?
Infantile Tay-Sachs disease – this is the most severe form and is most commonly seen in children younger than 2 years of age. Infants with infantile Tay-Sachs disease have seizures and become blind by 6 months of age. They also experience paralysis, loss of mobility, and loss of motor skills.
Juvenile Tay-Sachs disease – this is a less severe form that usually affects children between ages 4 and 8 years old. Children with juvenile Tay-Sachs disease have milder symptoms than those with infantile Tay-Sachs disease, such as muscle weakness and other neurological problems. As they get older, they may develop seizures or lose their ability to walk or speak clearly. Like infants with infantile Tay-Sachs disease, children with juvenile Tay-Sachs disease will eventually become blind.
Adult Tay-Sachs – adult forms of Tay-Sachs are more common than either type of childhood disease, but they are much less severe than the other two types. People who have adult forms of the disorder may not experience any symptoms for many years after birth.
What causes Tay-Sachs disease?
Tay-Sachs disease is caused by a genetic defect in a gene known as HEXA. This gene provides instructions for making an enzyme called beta-hexosaminidase A that breaks down gangliosides. In people with Tay-Sachs disease, the enzyme doesn’t break down gangliosides properly or at all. The build up of gangliosides leads to nerve cell death over time, resulting in progressive neurological dysfunction and disability that worsens over time.
Tay-Sachs disease is caused by a defect in a gene that produces an enzyme called hexosaminidase A. The enzyme breaks down GM2 ganglioside, a lipid that forms part of the structure of nerve cells. Without hexosaminidase A activity, GM2 ganglioside builds up and causes cell damage. Researchers believe that this build up occurs in the brain, spinal cord and retina at different times during development.
People with Tay-Sachs disease don’t have enough of the enzyme needed to break down GM2 ganglioside, so it builds up in their bodies and damages their cells.
What does it mean to be a Tay-Sachs carrier?
Carriers of Tay-Sachs disease have a 50% chance of passing on the disease to their children. They are also at risk for having another child with the disease. The carrier status can be passed down to future generations.
Tay-Sachs carriers may experience no or mild symptoms, or they may have severe symptoms and experience problems during pregnancy. However, the chances of the carrier passing on the disease is low if no affected siblings are born before 35 years of age.
If you’re pregnant and want to know whether you’re a carrier for Tay-Sachs disease, talk to your doctor about testing options that are available.
What are typical symptoms of Tay-Sachs disease?
Tay-Sachs disease is a progressive neurological condition that usually results in death by the time a child reaches the age of four.
The disease is caused by a deficiency of a lipid-related enzyme called hexosaminidase-A (Hex A). The lack of Hex A prevents the breakdown of substances called gangliosides, which are essential components of nerve cells and other tissues. Gangliosides are also involved in the production of cellular energy.
The first symptoms include:
- problems with movement, balance and coordination (motor skills)
- a steady decline in mental function
- vision problems
- difficulty swallowing, speaking and breathing
How do other forms of Tay-Sachs progress?
In the infantile form, which is more common in infants, symptoms start with a normal or abnormal head size. The head may look large and prominent (macrocephaly). This occurs because the brain is not developing normally.
As the disease progresses, children lose their ability to swallow, move, speak and breathe on their own. They become blind and deaf. Death usually occurs before age 5.
The juvenile form of Tay-Sachs disease affects teenagers and young adults. Symptoms include seizures; loss of muscle control (ataxia); dementia; blindness; and deafness. Lung problems are also common in this form of Tay-Sachs disease.
In the adult form of Tay-Sachs disease, symptoms may begin suddenly or slowly over time. Vision loss is often the first sign that something is wrong. Other common symptoms include dementia; difficulty walking; weakness in limbs; numbness or tingling sensations in hands or feet; speech problems; involuntary eye movements; and seizures that can occur without warning (drop attacks).
How is Tay-Sachs disease diagnosed?
Tay-Sachs disease is diagnosed by a doctor who examines the symptoms and does some tests to confirm the diagnosis.
The doctor will ask about your child’s medical history, including symptoms and any family members who have been diagnosed with Tay-Sachs disease. This may help determine if your child has inherited the condition or if it occurred spontaneously (by chance).
Your child may have:
A high level of hexosaminidase A in their blood and cerebrospinal fluid (the fluid surrounding the brain and spinal cord) after birth. This enzyme is part of an abnormal metabolic pathway that leads to build up of GM2 ganglioside in neurons, damaging them over time.
A characteristic cherry red spot on their retina, which appears at about 6 months of age and gradually enlarges. The spot is caused by degeneration of nerve cells in the retina due to the buildup of GM2 ganglioside.
Vision problems such as decreased vision or blindness due to damage from GM2 ganglioside accumulation in the optic nerves at around 3 years old for infants with type I syndrome (infants born with this condition), or later for those who develop it before age 2 years (milder form).
How can genetic counseling help families at risk for Tay-Sachs disease?
For families at risk for Tay-Sachs disease, genetic counseling can help answer questions and address concerns.
At-risk families face many decisions about whether to have children and how to manage the risk of passing on the disease. Genetic counselors help families understand their options and make informed decisions.
Genetic counseling is a confidential service that helps people learn about their family history, genetic risks and testing options. The goal is to empower people to make informed decisions about their health care, including reproductive choices and prenatal testing.
Genetic counselors provide information and support throughout the decision-making process, which can take weeks or months. The process begins with an initial consultation, which can be done over the phone or in person.
During this first visit, an extensive family history will be taken from both parents as well as any other family members who are available for contact. A pedigree chart will be created showing how each person is related to one another — such as siblings, aunts/uncles and cousins — so that genetic counselors can identify possible carriers of Tay-Sachs disease or other conditions within your family tree.
When should I do genetic testing for Tay-Sachs?
If you’re considering genetic testing for Tay-Sachs disease, you may want to know what the results could mean, and when it’s a good idea to do the test.
The most common reason people get tested for Tay-Sachs is if they or their partner has already had a child with the disease. If this is your situation, talk to your doctor about testing.
Tay-Sachs disease is an inherited disorder that causes nerve damage and brain degeneration. There’s no cure for it, and it’s usually fatal within a few years of onset.
Tay-Sachs testing can detect whether you carry one copy of the defective gene that causes the disease — but if you have two copies of this gene (one from each parent), it doesn’t matter whether you’re positive or negative on the test: You’ll still develop the disease.
How is Tay-Sachs disease treated?
There is no cure for Tay-Sachs disease, but treatment options can help relieve the symptoms and increase life expectancy.
Treatments and therapies are available to help people with Tay-Sachs disease:
Physical therapy. Exercises, stretching and other physical therapy techniques can help improve muscle strength, balance and coordination.
Occupational therapy. Occupational therapists teach you how to use adaptive equipment, such as hand splints or special computer software for people with visual impairments. They also provide tips on using everyday objects more easily.
Speech therapy. A speech therapist can teach you how to swallow safely and improve your speech if you have difficulty speaking because of weakness in your mouth or tongue muscles. You may need to learn how to use an alternative communication device such as a computer tablet or an eye gaze system that lets you select letters on an electronic tablet by looking at them instead of touching them with your hands.