Molecular (DNA) test to confirm common pathogenic and pseudodeficiency mutations for Tay Sachs disease. For initial testing for Tay Sachs, refer to Hexosaminidase A Percent and Total Hexosaminidase in Leukocytes (2008125). For carrier screening of common Ashkenazi Jewish-related diseases, please refer to Ashkenazi Jewish Diseases (BLM, ASPA, IKBKAP, FANCC, GBA, MCOLN1, SMPD1, HEXA), Common Mutation Panel (0051415).
- Patient Preparation
- Lavender (EDTA), pink (K2EDTA), or yellow (ACD Solution A or B).
- Specimen Preparation
- Transport 3 mL whole blood. (Min: 1 mL)
- Storage/Transport Temperature
- Unacceptable Conditions
- Ambient: 72 hours; Refrigerated: 1 week; Frozen: Unacceptable
Characteristics: Lysosomal storage disease that in its severe form leads to loss of motor skills beginning at three to six months of age that progresses to blindness, seizures and total incapacitation and death by 4 years of age. A milder disease with later onset and slower progression is seen in affected adults. Adult-onset Tay-Sachs is associated with variable neurological findings including: progressive dystonia, spinocerebellar degeneration, motor neuron disease and bipolar form of psychosis.
Incidence: 1 in 3000 Ashkenazi Jewish individuals, unknown in other ethnicities.
Inheritance: Autosomal recessive.
Cause: PathogenicHEXA gene mutations.
Mutations Tested: Four severe (7.6kb del, c.1073(+1)G>A, p.Y427Ifs (c.1274_1277dup TATC) c.1421(+1)G>C; one mild p.G269S (c.805G>A); and two pseudodeficiency alleles p.R247W (c.739C>T) and p.R249W (c.745C>T).
Clinical Sensitivity: 94 percent in Ashkenazi Jewish individuals, unknown in other ethnicities.
Methodology: Multiplex polymerase chain reaction and Detection Primer Extension
Analytical Sensitivity and Specificity: Greater than 99 percent.
Limitations: HEXAmutations other than those specified above will not be detected. Diagnostic errors can occur due to rare sequence variations.
Counseling and informed consent are recommended for genetic testing. Consent forms are available online.
|Component Test Code*||Component Chart Name||LOINC|
|0051430||Tay-Sachs Disease (HEXA) 7 Mut, Allele 1||38900-7|
|0051431||Tay-Sachs Disease (HEXA) 7 Mut, Allele 2||38900-7|
|0051432||Tay-Sachs Disease (HEXA) 7 Mut, Interp||51773-0|
|2001315||Tay-Sachs Disease (GBA) 7 Mut, Specimen||31208-2|
- Hexosaminidase A
- Hexosaminidase A Deficiency DNA assay
- TSD molecular assay