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HEREDITARY MONOGENIC DISEASES

           

Tay-Sachs disease

GM2 gangliosidosis or Tay-Sachs disease G2 gangliosides accumulation due to a deficiency in hexosaminidase characterized A.

The prevalence of the disease is 1 in 3,900 births among Jews and 1 in 320,000 births among non-Jewish people.

Three variants have been described based on the age of onset of the disease:

The infantile form (type 1) begins between 3 and 6 months old. The earliest symptom is continuous jolts in response to noise. Psychomotor retardation appears beyond 8 months with hypotonia, amaurosis and megalencephaly. There may be a stain cherry red in the macula. Muscle weakness progresses and ends in paralysis. This degenerative disorder ends in a stage of decerebration with fatal outcome during childhood. The enzymatic activity of the hexosaminidase A is either extremely low or totally absent leukocytes and cultured fibroblasts obtained from skin biopsy.

In the juvenile form (type 2), the onset of the disease is between 2 and 6 years with ataxia, behavioral disorders and a progressive loss of intellectual abilities that lead to a state of descerebración and death around 15 year old. The decreased activity of hexosaminidase A is less marked than in the infantile form.

Chronic adult form (type 3) may begin around age 10 but often the disorder is not diagnosed until adulthood.

The Tay-Sachs disease is transmitted as an autosomal recessive. The responsible gene (HEXA) encodes the alpha subunit of hexosaminidase A and is located on chromosome 15 (15q23). In populations at high risk (descendants of Ashkenazi Jews) is recommended to determine heterozygous individuals and prenatal diagnosis proceed.

There is no effective treatment for Tay-Sachs disease but can be administered AEDs. It is currently investigating a treatment for forms of slow progression aimed at inhibiting the synthesis of gangliosides.

GENE OR REGION STUDIED


  • HEXA