Tay-Sachs Disease (TSD, Hexosaminidase A deficiency)
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Tay-Sachs disease is an inherited disease named after the British ophthalmologist Warren Tay (1843-1927)  and  American neurologist Bernard Sachs (1858-1944) who described the features of the disease. Persons with Tay-Sachs disease have a deficiency of the enzyme hexosaminidase A that helps break down a substance known as GM2 ganglioside. Subsequently toxic quantities of GM2 accumulate throughout the body causing severe neurologic disease.

In its most common form infants with TSD disease develop normally for the first six months of life. As GM2 builds up in tissues and brain the child develops weakness, loss of motor skills, increased startle response, seizures, spasticity, blindness, paralysis, and inability to swallow. A cherry red spot can be seen on the retina of more than 90% of patients. Death usually occurs before the age of 5.

Late onset Tay-Sachs disease is a rare form of TSD with onset during childhood or adolescence characterized by poor coordination, weakness of the trunk muscles, tremor, slurred speech, and in some patients psychiatric disorders .

TSD is inherited in an autosomal recessive pattern, meaning two copies of the mutated gene must be present to develop the disorder. The carrier rate for TSD in the general population is 1 in 300. The carrier rate in individuals of Eastern European and Askhenazi Jewish descent is 1 in 30. The carrier rate is also increased in French Canadians and the Cajun population of Louisiana.

Potential carriers of TSD can be identified by a blood test that measures beta-hexosaminidase A activity. Activity of the enzyme is less than 55% in carriers of TSD. If both parents are found to be carriers testing can be performed for beta-hexosaminidase activity in fetal cells obtained by chorionic villus sampling or amniocentesis
 

Created 6/29/2007 Mark Curran, M.D. FACOG


 

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