Facebook Pixel Code
Section banner image
Paediatric Laboratory Medicine

Tay-Sachs Disease: HEXA Sequencing

Clinical Significance

Tay-Sachs disease (TSD) is characterized by progressive weakness and loss of motor skills beginning between three and six months of age. Over time, signs of progressive neurodegeneration occur, such as seizures, blindness, and paralysis, usually leading to death before the age of four. TSD is caused by a deficiency of the enzyme hexosaminidase-A (Hex-A). Deficiency of the Hex-A enzyme can also be identified by biochemical enzyme tests. TSD is an AR disorder caused by mutations in the HEXA gene, located on chromosome 15 (15q23-q24). Three mutations in the HEXA gene account for more than 99% of the mutations seen in AJ individuals affected with TSD. TSD is also seen at a comparable frequency in other ethnic groups including French Canadians and Cajuns. Two mutations that are seen more frequently in the French Canadian population are also screened for as part of this panel.

Test Name

Tay-Sachs Disease: HEXA Sequencing

Alternate Name/ Synonym

  • TSD
  • Hexosaminidase A deficiency
  • HEXA deficiency

Gene Name

  • HEXA

Alternate Gene Name


Test Code



Molecular Genetics



External Proficiency Testing


Turn Around Time

2 weeks (Prenatal samples), 2-3 weeks (Pregnancy/Urgent samples), 4-6 weeks (Routine)


Hexosaminidase A


Tay-Sachs Disease (part of the Ashkenazi Jewish screening panel)

Specimen Type

Blood; gDNA. 

For details about specimen requirements, please refer to: Specimen Type & Requirements (PDF).

Minimum Specimen Requirements

5-10 mL EDTA or ACD 0.5 mL EDTA (neonate); minimum 10 ug in 100 uL low TE (pH8.0)


Room Temperature

Special Requirements

Special Instructions for Genome Diagnostics Samples

If sample shipment >48 hours, ship on ice.

Approval is not required

CPT Codes


Shipping and Contact Information

The Hospital for Sick Children
Rapid Response Laboratory
170 Elizabeth Street, Room 3642
Toronto, ON
M5G 2G3
Phone: 416-813-7200
Phone: 1-855-381-3212


Interpretation is provided in report