Tay-Sachs disease

Tay-Sachs disease is a rare genetic disorder passed from parents to child. It's caused by the absence of an enzyme that helps break down fatty substances. These fatty substances, called gangliosides, build up to toxic levels in the brain and spinal cord and affect the function of the nerve cells.

In the most common and severe form of Tay-Sachs disease, signs and symptoms start to show up at about 3 to 6 months of age. As the disease progresses, development slows and muscles begin to weaken. Over time, this leads to seizures, vision and hearing loss, paralysis, and other major issues. Children with this form of Tay-Sachs disease typically live only a few years.

Less commonly, some children have the juvenile form of Tay-Sachs disease and may live into their teen years. Rarely, some adults have a late-onset form of Tay-Sachs disease which is often less severe than forms that begin in childhood.

If you have a family history of Tay-Sachs disease or if you're a member of a high-risk group and plan to have children, health care providers strongly recommend genetic testing and genetic counseling.

There are three forms of Tay-Sachs disease: infantile, juvenile and late onset/adult.

Infantile form

In the most common and severe form, called infantile form, an infant typically begins showing signs and symptoms by about 3 to 6 months of age. Survival is usually only a few years. Signs and symptoms can include:

• Exaggerated startle response when the baby hears loud noises
• "Cherry-red" spots in the eyes
• Loss of motor skills, including turning over, crawling and sitting up
• Muscle weakness, progressing to paralysis
• Movement problems
• Seizures
• Vision loss and blindness
• Hearing loss and deafness
• Problems swallowing
• Loss of mental functions and a lack of response to surroundings
• Growth in head size (progressive macrocephaly)

Juvenile form

The juvenile form of Tay-Sachs disease is less common. Signs and symptoms vary in severity and begin in childhood. Survival is typically into the teen years. Signs and symptoms can include:

• Behavior problems
• Gradual loss of skills and movement control
• Frequent respiratory infections
• Slow loss of vision and speech
• Decline in mental function and responsiveness
• Seizures

Last onset/adult form

This is a rare and less severe form with signs and symptoms beginning in late childhood to adulthood. Severity of symptoms varies greatly, and this form does not always impact life expectancy. Signs and symptoms progress slowly and can include:

• Muscle weakness
• Clumsiness and loss of coordination
• Tremors and muscle spasms
• Loss of the ability to walk
• Problems speaking and swallowing
• Psychiatric disorders
• Sometimes loss of mental function

When to see a doctor

If you or your child has any of the signs or symptoms that may indicate Tay-Sachs disease, or if you have concerns about your child's development, schedule an appointment with your health care provider.

Tay-Sachs disease is a genetic disorder that is passed from parents to their children. It occurs when a child inherits a flaw (mutation) in the HEXA gene from both parents.

The genetic change that causes Tay-Sachs disease results in a deficiency of the enzyme beta-hexosaminidase A. This enzyme is required to break down the fatty substance GM2 ganglioside. The buildup of fatty substances damages nerve cells in the brain and spinal cord. Severity and age of onset of the disease relates to how much enzyme is still produced.

Because the gene change that causes Tay-Sachs disease is found more often in certain populations, risk factors for Tay-Sachs disease include having ancestors from:

• Eastern and Central European Jewish communities (Ashkenazi Jews)
• Certain French Canadian communities in Quebec
• Cajun community of Louisiana
• Old Order Amish community in Pennsylvania

A blood test can be used to identify carriers of the HEXA gene change that causes Tay-Sachs disease. Genetic counseling is recommended following testing.

To confirm that your child has Tay-Sachs disease, your health care provider will ask about symptoms and any family hereditary disorders, and also do a physical exam. Your child may need to see a neurologist and an ophthalmologist for nervous system and eye examinations.

Your health care provider may order the following tests:

• Diagnostic blood test. The blood test checks the levels of hexosaminidase A enzyme in the blood. The levels are low or absent in Tay-Sachs disease.
• Genetic testing. This test can examine the HEXA gene to identify whether there are changes that indicate Tay-Sachs disease.
• Eye exam. During an eye exam, the health care provider may see a cherry-red spot in the back of the eyes, which is a sign of the disease.

Prenatal testing for Tay-Sachs disease can be done during pregnancy by removing a tiny piece of the placenta (chorionic villi sampling) or by removing a small sample of the amniotic fluid around the baby (amniocentesis).

There is no cure for Tay-Sachs disease, and no treatments are currently proved to slow progression of the disease. Some treatments can help in managing symptoms and preventing complications. The goal of treatment is support and comfort.

Supportive treatments include:

• Medication. A number of prescription medications are available to reduce symptoms and prevent complications: for example, anti-seizure medications or antibiotics for infection.
• Respiratory care. Accumulated mucus in the lungs is common and results in a high risk of lung infections that cause breathing problems. Chest physiotherapy (CPT), exercise and other techniques can help remove mucus from the lungs. Medications to reduce saliva production and positioning techniques are also options to reduce the risk of mucus accumulation and prevent aspiration pneumonia.
• Nutrition and hydration. Your child may have trouble swallowing or develop respiratory problems by inhaling food or liquid into the lungs while eating. To prevent those problems, your doctor may recommend an assistive feeding device such as a feeding tube. A feeding tube may be inserted through your child's nose and into the stomach, or a surgeon may surgically insert a feeding tube directly into the stomach (gastrostomy tube).
• Physical therapy. As the disease progresses, your child may benefit from physical therapy to help keep joints flexible and maintain as much ability to move (range of motion) as possible. Physical therapy may delay joint stiffness and reduce or delay the loss of function and pain that can result from affected muscles.
• Occupational therapy. These therapists can recommend activities and supportive devices to help with daily functioning.
• Speech and language therapy. Speech and language therapists can assist with swallowing problems.

Potential future treatments

Research on treatments such as gene therapy, stem cell transplantation, or enzyme replacement therapy may eventually lead to a cure or treatment to slow the progression of Tay-Sachs disease.

Ask your child's health care provider to suggest resources and information to help you and your family cope with your needs. Look for local support groups to connect you with other families who are sharing similar challenges.