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Tay Sachs Disease Fact Sheet

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					                                                           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.




Tay-Sach Disease                                                        Pg. 1
                                                           Jose L. Guzman III




         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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                                                         Jose L. Guzman III

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



Tay-Sach Disease                                                      Pg. 3
                                                            Jose L. Guzman III


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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                                                           Jose L. Guzman III


   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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                                                        Jose L. Guzman III


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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