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Tay-Sachs Disease via the French Canadian Deletion in the HEXA Gene

Summary and Pricing

Test Method

Targeted Deletion Testing via PCR
Test Code Test Copy GenesTest CPT Code Gene CPT Codes Copy CPT Codes Base Price
1450 HEXA 81479 81479 $250 Order Options and Pricing
Test Code Test Copy Genes Test CPT Code Gene CPT Codes Copy CPT Code Base Price
1450HEXA81479 81479 $250 Order Options and Pricing

An additional 25% charge will be applied to STAT orders. STAT orders are prioritized throughout the testing process.

Turnaround Time

18 days on average for standard orders or 14 days on average for STAT orders.

Please note: Once the testing process begins, an Estimated Report Date (ERD) range will be displayed in the portal. This is the most accurate prediction of when your report will be complete and may differ from the average TAT published on our website. About 85% of our tests will be reported within or before the ERD range. We will notify you of significant delays or holds which will impact the ERD. Learn more about turnaround times here.

EMAIL CONTACTS

Genetic Counselors

Geneticist

  • Jana Paderova, PhD

Clinical Features and Genetics

Clinical Features

Tay-Sachs disease (TSD), also known as GM2 Gangliosidosis Type 1, is a neurodegenerative lysosomal storage disorder due to deficiency in the enzyme beta-hexosaminidase A. The enzymatic deficiency results in the accumulation of the lipid GM2 ganglioside, the natural substrate for beta-hexosaminidase A, mainly in nerve cells of the brain and retina. Two main variants of TSD are recognized.

Infantile acute TSD is the most severe and most prevalent variant. It is characterized by onset before the age of 6 months, rapid progression and death by 4 years of age, usually from bronchopneumonia. Symptoms at onset include muscle weakness and atrophy, hypotonia, exaggerated startle response, cherry-red spot in the macula, and decline in psychomotor functions. Abnormal eye movements, visual difficulties and seizures of variable types occur later. Symptoms progress rapidly to blindness, deafness, and generalized paralysis, leading eventually to death (Gravel et al. In: Scriver et al. 2001).

Late-onset TSD is clinically heterogeneous in regards to the age of onset of symptoms, clinical features, and progression rate. It is further divided into subacute TSD and chronic TSD. In the subacute TSD, symptoms begin between 2-5 years of age and death occurs in the second decade of life, usually from infections. Symptoms include ataxia, loss of movement coordination, spasticity, dystonia, slow deterioration of speech, gait and posture, cerebellar atrophy, dementia, and loss of vision (Maegawa et al. 2006). In chronic TSD, age of onset varies from childhood to late adulthood. Symptoms include seizures, unsteady gait and slow neurological deterioration with cognitive loss and psychosis (Johnson 1981; Navon and Proia 1989).

Genetics

All TSD pathogenic variants are inherited in an autosomal recessive manner and result from mutations in the HEXA gene (Myerowitz and Hogikyan 1986). TSD occurs worldwide, with a carrier frequency of 1/250 in the general population. It is, however, more prevalent in the Ashkenazi Jewish and French Canadian populations with carrier frequencies of 1/30 and 1/14, respectively (Kaback 2000). 

A genomic deletion of 7.6 kb in the HEXA gene was found in about 80% of the disease alleles in Tay Sachs disease patients from the French Canadian population (Hetchman et al. 1990). This deletion includes the promoter, the entire exon 1 and part of intron 1 of the gene (Myerowitz and Hogikyan, 1986). 

The HEXA gene encodes the alpha-subunit of the beta-hexosaminidase A enzyme, which is involved in the biodegradation of GM2 ganglioside.

Clinical Sensitivity - Targeted Deletion

A genomic deletion of 7.6 kb in the HEXA gene was found in about 80% of the disease alleles in Tay Sachs disease patients from the French Canadian population (Hetchman et al. 1990).  

Testing Strategy

This test involves amplification of patient DNA with specific PCR primers that flank the deletion. Positive control samples include samples from two individuals from the French Canadian population, who are known to be heterozygous for the deletion. A healthy individual known to be a non-carrier of the deletion is included as a negative control.

Indications for Test

Candidates for this test are patients with a clinical diagnosis of Tay Sachs disease and biological relatives of patients who are known to have the French Canadian deletion in the HEXA gene. This test is recommended as a first step for patients of French Canadian origin.

Gene

Official Gene Symbol OMIM ID
HEXA 606869
Inheritance Abbreviation
Autosomal Dominant AD
Autosomal Recessive AR
X-Linked XL
Mitochondrial MT

Disease

Name Inheritance OMIM ID
Tay-Sachs Disease AR 272800

Related Test

Name
Tay-Sachs Disease via the HEXA Gene

Citations

  • Gravel RA, Kaback MM, Proia RL, Sandhoff K, Suzuki K and Suzuki K. 2001. The GM2 Gangliosidoses. In: Scriver et al. Eds 8 Vol 3 McGraw-Hill, New York, 3827-3877.
  • Hechtman P. et al. 1990. American Journal of Human Genetics. 47: 815-22. PubMed ID: 2220821
  • Johnson W.G. 1981. Neurology. 31:1453-6. PubMed ID: 7198192
  • Kaback M.M. 2000. European Journal of Pediatrics. 159 Suppl 3: S192-5. PubMed ID: 11216898
  • Maegawa G.H. et al. 2006. Pediatrics. 118: e1550-62. PubMed ID: 17015493
  • Myerowitz R., Hogikyan N.D. 1986. Science. 232: 1646-8. PubMed ID: 3754980
  • Navon R, Proia R.L. 1989. Science. 243: 1471-4. PubMed ID: 2522679

Ordering/Specimens

Ordering Options

We offer several options when ordering sequencing tests. For more information on these options, see our Ordering Instructions page. To view available options, click on the Order Options button within the test description.

myPrevent - Online Ordering

  • The test can be added to your online orders in the Summary and Pricing section.
  • Once the test has been added log in to myPrevent to fill out an online requisition form.
  • PGnome sequencing panels can be ordered via the myPrevent portal only at this time.

Requisition Form

  • A completed requisition form must accompany all specimens.
  • Billing information along with specimen and shipping instructions are within the requisition form.
  • All testing must be ordered by a qualified healthcare provider.

For Requisition Forms, visit our Forms page


Specimen Types

Specimen Requirements and Shipping Details

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ORDER OPTIONS

View Ordering Instructions

1) Select Test Method (Backbone)


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2) Select Additional Test Options

STAT and Prenatal Test Options are not available with Patient Plus.

No Additional Test Options are available for this test.

Note: acceptable specimen types are whole blood and DNA from whole blood only.
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