Tay-Sachs Disease ... (Tay-Sachs disease) - Gen HEXA.  

The Tay-Sachs disease is a rare inherited disorder that progressively destroys neurons in the brain and spinal cord.

The most common form of Tay-Sachs disease is evident in childhood. Children with this disorder usually appear normal until the age of 3 to 6 months, when development slows and muscles used for movement weaken. Affected children lose motor skills such as turning, sitting and crawling. Also they develop an exaggerated reaction to loud noises startle. As the disease progresses, children this disease experience seizures, loss of vision and hearing, mental retardation and paralysis. An eye anomaly with a dot cherry red color, is also characteristic of this disorder. Children with this severe childhood form of the disease do not live beyond early childhood.

There are other rare forms of the disease manifest themselves later manner. Signs and symptoms can appear in childhood, adolescence, or adulthood and are usually milder than those seen with the infantile form. Characteristic features include muscle weakness, ataxia and other problems with movement, speech problems and mental illness.

The Tay-Sachs disease results from mutations in the HEXA gene, located on the long (q) arm of chromosome 15 at position 24.1 (15q24.1). This gene encodes an enzyme called beta-hexosaminidase A, which plays a critical role in the brain and spinal cord. This enzyme is found in lysosomes. Within the lysosomes, the enzyme beta-hexosaminidase A helps break down a fatty substance called GM2 ganglioside.

We found over 120 mutations in the HEXA gene causing the Tay-Sachs disease. Mutations in the HEXA gene disrupt the activity of beta-hexosaminidase A, which prevents the enzyme decomposes GM2 ganglioside. As a result, this substance accumulates to toxic levels, in particular in neurons in the brain and spinal cord, causing the destruction of neurons.

This disease is inherited in an autosomal recessive pattern, that is, both copies of the gene in every cell must have mutations for alteration is expressed. The parents of an individual with an autosomal recessive disease have a copy of the mutated gene, but usually show no signs and symptoms of the disease.  

Tests in IVAMI: in IVAMI perform detection of mutations associated with Tay-Sachs disease, by complete PCR amplification of the exons of the HEXA gene, and subsequent sequencing.

Samples recommended: EDTA blood collected for separation of blood leukocytes, or impregnated sample card with dried blood (IVAMI may mail the card to deposit the blood sample).