Tay-Sachs disease

Overview

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.

Symptoms

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.

Causes

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.

Risk factors

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.