Tay-Sachs Disease

What is Tay-Sachs Disease ?

Tay-Sachs disease, the most common lipid storage disease, results from a congenital enzyme deficiency. It occurs in fewer than 100 infants born each year in the United States. It strikes people of Ashkenazic Jewish ancestry about 100 times more often than the general population, occurring in about 1 in 3,600 live births in this ethnic group. About 1 in 30 Ashkenazi Jews, French Canadians, and American Cajuns are heterozygous carriers of this defective gene. If two such carriers have children, each of their offspring has a 25% chance of having Tay-Sachs disease. The disease is characterized by progressive mental and motor deterioration and is always fatal, usually before age 5.

Causes of Tay-Sachs Disease

Tay-Sachs disease (also known as GM2 gangliosidosis) is an autosomal recessive disorder in which the enzyme hexosaminidase A is deficient. This enzyme is necessary for metabolism of gangliosides, water-soluble glycolipids found primarily in central nervous systew (CNS) tissues. Without hexosaminidase A, accumulating lipid pigments distend and progressively destroy and demyelinate CNS cells.

Signs & Symptoms of Tay-Sachs Disease

Note: That Tay Sachs symptoms usually refers to various symptoms known to a patient, but the phrase Tay Sachs signs may refer to those signs only noticable by a doctor:

• Loss of rolling over
• Cherry-red spot in the back of their eyes
• Muscle atrophy
• Loss of learned skills
• Loss of smiling
• Unable to swallow
• Deafness
• Dementia

Diagnostic Tests

Serum analysis showing deficient hexosaminidase A is typically the key to diagnosis. Diagnostic screening is essential for all couples of Ashkenazic Jewish ancestry and for others with a family history of the disease. A simple blood test evaluating hexosaminidase A levels can be used to identify carriers.

If carriers wish prenatal diagnosis, amniocentesis or chorionic villus biopsy can be used to detect hexosaminidase A deficiency and, thereby, Tay-Sachs disease in the fetus.

For two-carrier parents using invitro fertilization to achieve pregnancy, genetic testing has been attempted with some success. Healthy embryos are transferred to the woman's uterus.

Treatment

Tay-Sachs disease has no known cure. Supportive treatment includes tube feedings using nutritional supplements, suctioning and postural drainage to remove secretions, skin care to prevent pressure ulcers when the child becomes bedridden, and mild laxatives to relieve neurogenic constipation. Unfortunately, anticonvulsants usually fail to prevent seizures. Because these children need round-the-clock physical care, they commonly require long-term care in special facilities.

Prevention Tips

The enzyme defect that causes Tay-Sachs disease is present from the time of conception. There is no way to prevent the disease in children who have already been born.

There is no known way to prevent this disorder. However, genetic testing can detect carriers of the gene for this disorder and is recommended prior to conception for couples from at risk populations. Prenatal diagnosis is possible from amniotic fluid studies.