Tay-Sachs Disease

Disease characteristics
Tay-Sachs disease (TSD) is a genetic disorder, fatal in its most common variant known as Infantile Tay-Sachs disease. The disease occurs when harmful quantities of a fatty acid derivative called ganglioside accumulate in the nerve cells of the brain. Tay-Sachs disease is caused by mutations on the Hexasaminidase A (HEXA) gene on chromosome 15.

Prevalence
This mutation is the most prevalent mutation in the Ashkenazi Jewish population, and leads to the infantile form of Tay-Sachs disease. In the United States, about 1 in 27 to 1 in 30 Ashkenazi Jew is a recessive carrier.

Mutation
More than 90 mutations have been identified to date in the HEXA gene, and new mutations are still being reported. Each of these mutations alters the protein product, and thus inhibits the function of the enzyme in some manner. For example, a four base pair insertion in exon 11 (1278insTATC), results in an altered reading frame for the HEXA gene.

Testing criteria and symptoms
Being of Ashkenazi Jewish ancestry
Seizures, Noticeable behavior changes, such as the infant stops smiling, crawling or rolling over
Increased startle reaction, decreased eye contact, listlessness, slow body growth with increasing head size
Delayed mental and social skills