Jose L. Guzman III
Tay-Sachs Disease Fact Sheet:
Description/Etiology:
Tay-Sachs disease is a rare and fatally lysosomal lipid storage disorder
(lysosomes, the vesicles within the cell whose primary function is to
degrade the breakdown products of cellular metabolism). It is an
autosomal recessive disease caused by a deficiency of the enzyme
hexosaminidase A (Hex A) as a result of a mutation in the HEXA gene
found on chromosome 15.
The brain cells use Hex A to metabolize glycosphinogolipids (i.e. fatty
substances known as GM2 gangliosides). A deficiency of Hex A leads to
accumulation of GM2 gangliosides in the brain and spinal nerves, resulting
in progressive neurological deterioration.
The three forms of Tay-Sachs disease (TSD) are infantile, juvenile, and
adult, based on the age of onset of neurological symptoms.
1. Infantile TSD: is the most common form, with signs appearing during
the first 6 months of life and include an eye abnormality called a
cherry-red spot. This cherry-red spot is a red spot seen in the macula
area of the retina (There is cloudiness of retina, except in fovea
region ). Once signs are present, the disease progresses quickly,
resulting in death around the age of 4 to 5 years.
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Figure 1. Cherry spot on macula with Tay-Sach disease
2. Juvenile TSD: presents between the ages of 2 and 10 years and
progresses more slowly than infantile. Their life expectancy is about
5 to 15 years.
3. Adult-onset: also called late-onset TSD, occurs during the twenties
or early thirties and is a milder form. The ability of these patients to
produce a small amount of Hex A is retained, unlike the other forms
where the enzyme production is completely absent.
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Facts and Figures:
Tay-Sach disease can be inherited only if both parents carry the
recessive gene mutation. 1 in 25 persons of Ashkenazi Jewish descent are
carriers of the genetic mutation. In the general population , about 1 in 250
people are carriers. About 80% of individuals diagnosed are of Jewish
ancestry, although sporadic cases appear in non-Jewish populations.
Tay-Sach disease is named after, Warren Tay, founding member of the
British Ophthalmologic Society in 1881, when he described symmetrical
changes in the yellow spot region of the macula of infants with
neurological impairment.
Risk factors:
People most at risk include those of Ashkenazi Jewish, French
Canadian, Pennsylvania Dutch , or American Cajun descent and those
with family history of Tay-Sach disease. Genetic counseling should be
offered to those already pregnant or planning to have a family at high risk
for the disease. Some states require screening once the newborn is born.
Clinical Presentation/Signs and symptoms:
Signs and symptoms in the infantile form of TSD include poor head and
neck support, cherry-red spots on macula, deafness, blindness, difficulty
swallowing, and impaired developmental and motor skills due to muscle
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atrophy (wasting). Juvenile TSD includes speech difficulties, cognitive and
motor difficulties, dysphagia (swallowing difficulties), spasticity, and
unsteady gait. Adult TSD symptoms include unsteady gait, spasticity,
speech and swallowing difficulties, cognitive difficulties, and
schizophrenic-like psychosis.
Diagnosis:
Enzyme assay tests of the white blood cells, serum, and or other tissues
samples may reveal abnormally low levels of Hex A or absence of Hex A
enzyme. Amniotic fluid can be tested prenatally on the pregnant woman.
Risk factors should be assessed, including family history, ethnic and racial
descent. On physical exam, an infant may not be able to sit up or roll over
without support by 1 year of age. The child’s ophthalmological exam
typically reveals a cherry-red spot on the macula. On exam, the patient’s
motor skills, mental status, vision, and hearing may show abnormalities in
TSD. The infant’s growth and development may be delayed or abnormal
in TSD.
Treatment:
There is no cure for Tay-Sach disease. Treatment is supportive, focusing
primarily on symptom management. The goals of treatment for this
population are to maintain optimum physiological status and prevent
complications.
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These patients may need to have their vitals monitored, nutritional and
respiratory status, and skin integrity monitored to prevent complications.
They may need laxatives for constipation, antibiotics for infection, and
anticonvulsants for seizures. They may have physical therapy to improve
motor skills and decrease spasticity. A wheelchair or other orthopedic
supportive devices may be needed for patients with impairment. While
infants diagnosed with TSD are not expected to live past 5 years of age,
the life expectancy in adult-onset TSD is variable, and some adults can
live a full life.
Parents and family member of those affected with Tay-Sach disease
should be assessed for coping ability. They should be educated about the
pathophysiology, potential complications, treatment risks and benefits.
They should be offered social workers to assists in identification of support
groups, hospice, in-home services, or religious representation for
counseling.
There is several research therapeutic approaches being trial to treat
this lysosomal storage disease, but are still being investigated. These
include enzyme replacement therapy, bone marrow transplantation,
neural stem therapy, and molecular and pharmacological therapy.
Researchers still have much to learn. Because Tay-Sach disease affects
the central nervous system, many believe that no single approach will be
the solution.
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References:
Anderson, L. (2007). Tay-Sach Disease. MedlinePlus Medical Encyclopedia.
Retrieved June 30, 2009, from
http://www.nlm.nih.gov/medlineplus/ency/article/001417.htm
Goldberg, S., Trattler, W. Ophthalmology Made Ridiculously Simple.
Interactive edition, 4th ed. Miami, FL: MedMaster Inc, 2009: 51.
McCance, K., Huether, S. Pathophysiology: The Biologic Basis for Disease in
Adults and Children, 6th ed. ST. Louis, MO: Mosby, 2006: 579.
Shapiro, B., Hatters-Friedman,F., Fernandes-Filho, J., Anthony, K., &
Natowicz, M. (2006) Late-onset Tay-Sachs disease: Adverse effects on
medications and implications for treatment. Neurology, 67(5)875-877.
Suvarna JC, Hajela SA. Cherry-red spot. J Postgrad Med 2008;54:54-7
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