Tay Sachs disease (TSD) is a rare type of genetic mutation that destroys the nervous system. Symptoms of the disease usually begin in infancy and result in the death of the child by age 5. The mutated gene causes the lack, or reduced production, of the enzyme hexosaminidase A (HEXA), which processes certain fats. Without HEXA, these fats build up, damaging cells in the central nervous system.

There are three different forms of TSD: infantile, juvenile and late-onset. The infantile form is the most common, and children with the condition do not produce any HEXA. The juvenile form is also fatal to the child with death usually occurring by age 15. The late-onset form results in a much slower deterioration of the central nervous system, and patients may live past age 60 because they produce small amounts of HEXA. People may also be carriers of the genetic mutation. Carriers do not have the symptoms but do have the ability to pass the gene to biological children.

Tay Sachs disease, while rare, most commonly occurs in people of eastern European descent, particularly eastern European (Ashkenazi) Jewish populations. It is also more common among certain Louisiana Cajun and French-Canadian populations. However, people of either gender from any ethnic background may have the genetic mutation that causes TSD.

Common signs and symptoms of TSD include red spots in the retina of the eye, an increased startle reflex in infants, seizures, deafness, blindness and paralysis. There is no cure for TSD. Treatments involve making the patient more comfortable. The late-onset form may be treated with a variety of medications to control a patient’s specific symptoms.

Tay Sachs disease (TSD) is a genetic mutation that causes an absence or defect in the gene that produces an enzyme called hexosaminidase A (HEXA). HEXA allows the body to break down certain fatty substances in the brain and nerve cells. Without the enzyme, these fats build up in the body and eventually cause the destruction of the central nervous system. Children born with the most common form of the disease (infantile) typically die by the age of 5 or 6 years.

The nervous system cells and tissues are damaged by the buildup of fatty substances. These fats (GM2 ganglioside) build up in the cells and over time cause degeneration and loss of function in the brain, peripheral nervous system, liver, spleen and bone marrow. People with the disease develop muscle weakness and deterioration of nerves throughout the body.

TSD is a rare condition that occurs most commonly in people of eastern European descent (particularly eastern European Ashkenazi Jews), as well as certain Louisiana Cajun and French-Canadian populations. In the Ashkenazi population, about one in 30 people are carriers of TSD, while in the general population about one in 300 people are carriers, according to the National Institutes of Health. However, the disease can affect a person of either gender or any ethnic background. People may be carriers of the genetic mutation and never develop the disease. Children of carriers may also pass the mutation to the next generation.

There are three forms of Tay Sachs disease (TSD), with the most common form affecting infants. The juvenile and late-onset forms of TSD have been identified recently and are much rarer.

• Infantile TSD. This is the most common form of the disease and people with it do not produce the enzyme hexosaminidase A (HEXA). Infants with TSD usually develop normally for the first few months of life, after which mental and physical abilities begin to deteriorate. The infant has seizures, develops red spots in the retina of the eye, and becomes blind, deaf and paralyzed. Children with TSD usually die from recurring infections by age 5 or 6.
  
  
• Juvenile-onset TSD. People who have this condition do produce HEXA but in inadequate amounts. Symptoms are similar to the infantile form, but do not appear until the child is between 2 and 5 years old. The disease progression is slower in this form, but the outlook for the child is fatal. Death usually occurs by age 15.
  
  
• Late-onset TSD. Similar to the juvenile form, people with this condition produce small amounts of the enzyme HEXA. As a result, the symptoms of the disease do not become apparent until later in life. Symptoms develop during the 20s and 30s and cause an unsteady walk and slow deterioration of the central nervous system, which worsens over time. Some adults with late-onset TSD survive until ages 60 to 80 years.

Tay Sachs disease (TSD) is caused by an absence or defect in genes that produce the enzyme hexosaminidase A (HEXA), which breaks down certain fatty substances (GM2 gangliosides) in brain and nerve cells. Without the enzyme, these fats build up in brain and nerve cells and cause the nervous system to stop functioning. It is a genetic mutation that can affect any population, but is more common among people of eastern European ancestry.

TSD is controlled by one specific pair of genes (on chromosome 15), which produce HEXA when active. When one or both of these genes function properly, then enough HEXA can be produced by the body. If one of the genes is inactive, then that person is a carrier of TSD.

Tay Sachs disease (TSD) usually develops in infancy, with symptoms appearing at 4 months to 6 months of age. Infants with TSD develop normally for the first 3 months to 6 months of age. After this time, the absence of the enzyme hexosaminidase A (HEXA) causes development to slow. Normal developmental milestones may not be achieved at the appropriate age, such as smiling and crawling. Developmental milestones that were achieved earlier may begin to decline.

Other signs and symptoms of TSD include:

• Cherry-red spots in eyes
• Seizures
• Increased startle reflex
• Unsteady walk
• Dementia
• Muscle weakness
• Loss of vision, blindness
• Paralysis
• Deafness
• Inability to swallow
• Mental illness
• Problems speaking

There is no cure for Tay Sachs disease (TSD). Treatment usually involves ensuring the patient is comfortable and controlling symptoms. The infantile form of TSD is fatal, with death usually occurring by age 5 or 6. The juvenile form is also fatal, but with the slower progression of the disease death may not occur until age 15. Anticonvulsant medications may be prescribed to reduce the incidence seizures in some young patients.

Due to the presence (even though in inadequate amounts) of the HEXA enzyme, late-onset TSD progresses more slowly than the other forms. Similar to the infantile and juvenile forms, there is no specific treatment, but adults with the disease may be treated with a variety of medications to manage specific symptoms.

Prevention methods are currently the only manner of ensuring a child will not be born with Tay Sachs disease. These methods usually involve testing the fetus once a woman is pregnant or testing both prospective parents for the genetic mutation before pregnancy occurs. Should the fetus test positive, a recommendation for terminating the pregnancy may follow.

Genetic testing can be performed before pregnancy in order to identify whether either prospective parent is a carrier of the disease. Genetic testing may allow women to decide whether to become pregnant, or to identify the risk of passing the Tay Sachs disease gene to future children. Genetic testing involves a blood test of both prospective parents to identify mutations or changes in the genes.

Chorionic villi sampling is a form of prenatal testing that can also be used to identify the presence or absence of the HEXA enzyme. It is performed at some point during the 10^th through 12^th week of pregnancy by removing a small cell sample from the placenta.

Amniocentesis is a form of prenatal testing commonly used to identify many genetic disorders, including a fetus lacking the HEXA enzyme. It is normally performed at some point during the 15^th through 18^th week of pregnancy. A needle is used to draw a small sample of the uterine amniotic fluid surrounding the fetus. The fluid is then tested for HEXA.

There is ongoing research on Tay Sachs disease (TSD) that is devoted to improving diagnosis and treatment methods for TSD. Enzyme replacement therapy is being explored in order to provide the enzyme hexosaminidase A (HEXA) that is lacking in people born with the disease. The therapy has not been successful due to problems with the central nervous system accessing the enzyme. Scientists are continuing to research enzyme therapies.

Bone marrow transplantation has been investigated as a possible treatment. However, it has not been successful in either reversing the central nervous system damage or slowing it down. Research on bone marrow transplantation is continuing.

Preparing questions in advance can help patients and parents have more meaningful discussions with their physicians regarding their or their child’s treatment options. The following questions related to Tay Sachs disease (TSD) may be helpful:

1. I am a carrier of the TSD gene. Should I have genetic tests before pregnancy?
   
   
2. My parent was a carrier of the TSD gene. Should I have a genetic test?
   
   
3. I just had an amniocentesis that indicated my fetus has TSD. What are my options?
   
   
4. I have a child with TSD. What can be done to make him or her more comfortable?
   
   
5. My child is no longer crawling and smiling like he or she was a few months ago. Could it be TSD?
   
   
6. My child has TSD. What type of the disease does he or she have?
   
   
7. My child has TSD and is experiencing seizures. What can be done to treat these?
   
   
8. I have late-onset TSD. Are there any lifestyle management techniques I can make to improve my life expectancy?
   
   
9. How did my child get TSD when I do not have any family history of the condition?
   
   
10. Are any advances being made in the use of enzymes to treat TSD?