Definition

Tay-Sachs disease (TSD) is a fatal genetic disorder. It occurs when harmful amounts of ganglioside GM2, a fatty substance, accumulate in the brain's nerve cells causing progressive destruction . There are infantile-, juvenile-, and adult-onset forms. Given the best of care, all children with the infantile form of TSD die by the age of five.

Causes

TSD is caused by the absence of the enzyme beta-hexosaminidase A. This enzyme breaks down GM2. TSD is controlled by a pair of genes on chromosome 15. Those who have one copy of an active gene and one copy of an inactive gene are called TSD carriers. TSD occurs when both parents pass on the inactive gene to their child.

Genetic Material

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Risk Factors

A risk factor is something that increases your chance of getting a disease or condition. Risk factors include:

• Having parents who are carriers of the TSD gene
• Race: Eastern European (Ashkenazi) Jewish descent. TSD is also frequently found in French Canadian and Cajun populations.

Symptoms

Babies with TSD may seem to develop normally until about 4 to 5 months of age when there is an arrest of development and symptoms begin to occur. Symptoms may include:

• Floppy body position
• Shrill cry
• Decreased eye contact
• Increased startle reaction
• Loss of motor skills
• Enlarged head
• Vision loss or blindness
• Deafness
• Difficulty swallowing
• Slurred speech (juvenile-onset form)
• Muscular difficulties, such as:
  • Spastic muscles
  • Weakness or paralysis
• Mental retardation
• Seizures

Diagnosis

The doctor will ask about your child's symptoms and medical history, and perform a physical exam. The doctor may examine your child's eyes to look for a cherry red spot on the retina that may occur in TSD.

A blood test to measure hexosaminidase A activity can also help diagnose TSD.

Treatment

There is presently no treatment for TSD. However, research is ongoing into different therapeutic modalities, such as substrate deprivation.

Prevention

There are no known ways to prevent Tay-Sachs disease once a person is born. If you are a carrier of the inactive gene that causes TSD, you can talk to a genetic counselor before deciding to have children. Prenatal testing during the first trimester is available.