What is Tay – sachs disease?
• A rare inherited genetic disorder that progressively
destroys nerve cells (neurons) in the brain and spinal
cord, most commonly occurring in children.
• A disease where your lysosomes (use enzymes to break
down extra stuff in your body and recycle it) aren't
working right due to the absence of the enzyme
Without Hex-A, a fatty substance, or lipid, called GM2 ganglioside
accumulates abnormally in cells, especially in the nerve cells of the
brain. This ongoing accumulation causes progressive damage to the
What is Tay – sachs disease?
•People with Tay-Sachs don't
have the DNA instructions to
make Hex-A correctly: usually
they make the Hex-A, but
something is wrong with the
hooks that the cell uses to
move the Hex-A around
inside the cell.
•Tay-Sachs disease results
from defects in a gene on
chromosome 15 that codes
for production of the enzyme
Hex-A. We all have two
copies of this gene.
What is tay – sachs disease?
• This condition is inherited in an autosomal
recessive pattern, which means both copies of
the gene in each cell have mutations.
• The parents of an individual with an autosomal
recessive condition each carry one copy of the
mutated gene, but they typically do not show
signs and symptoms of the condition.
• It's a disease you get in your DNA from your
parents, and both your mother and your father
have to have the disease in their DNA in order for
you to get it.
• It is not catching.
• Mutations in the HEXA gene disrupt the activity of
beta-hexosaminidase A (prevents the enzyme from
breaking down GM2 ganglioside).
• The HEXA gene provides instructions for making part
of an enzyme called beta-hexosaminidase A, which
plays a critical role in the brain and spinal cord.
• This enzyme is located in lysosomes, which are
structures in cells that break down toxic substances
and act as recycling centers.
• Within lysosomes, beta-hexosaminidase A helps
break down a fatty substance called GM2
• As a result, this substance accumulates to toxic
levels, particularly in neurons in the brain and spinal
• Progressive damage caused by the buildup of GM2
ganglioside leads to the destruction of these
neurons, which causes the signs and symptoms of
• Because Tay-Sachs disease impairs the function of a
lysosomal enzyme and involves the buildup of GM2
ganglioside, this condition is sometimes referred to
as a lysosomal storage disorder or a GM2-
The cherry red spot
• One of the signs of Tay-Sachs is the presence of a cherry-red
• The center of the fovea appears bright red because it is
surrounded by a milky halo.
• This halo represents loss of retinal transparency which comes
from a pile up of ganglioside in ganglion cells.
• The ganglioside accumulates because its catabolic enzyme
(hexosaminidase A) is missing. Remember that there are no
ganglion cells in the center of the fovea, so that the
underlying choroid transmits its red color.
• A similar metabolic cherry-red spot occurs in other lysosomal
enzyme deficiences such as generalized gangliosidosis (GM 1),
Sandhoff's, Gaucher's, mucolipidosis Types 1 and 2, Niemann-
Pick Type A, and multiple sulfatase deficiency. Vision is usually
subnormal because the ganglion cells are not working
• Rapidly declining development
• Weakening of muscles
• Loss of motor skills
• They develop an exaggerated startle reaction to loud noises
• Inability to swallow or chew
• Mental retardation
Note: Leads to death at the age of 4 – 5 years old.
• In children, the destructive process begins in the
fetus early in pregnancy.
• However, a baby with Tay-Sachs disease appears
normal until about six months of age when its
• By about two years of age, most children
experience recurrent seizures and diminishing
• The infant gradually regresses, and is eventually
unable to crawl, turn over, sit or reach out.
Eventually, the child becomes blind, cognitively
impaired, paralyzed and non-responsive.
• By the time a child with Tay-Sachs is three or four
years old, the nervous system is so badly affected
that death usually results by age five.
• A much rarer form of Tay-Sachs, Late-Onset Tay-Sachs
disease, affects adults and causes neurological and
• The disease has not been extensively described.
• As for the childhood form of Tay-Sachs, there is no
• Treatment involves managing the symptoms of the