Tay-Sachs Disease (HEXA), 7 Variants

Background information for Tay-Sachs Disease (HEXA), 7 Variants:
Characteristics: Tay-Sachs disease is a lysosomal storage disease that, in the most severe childhood-onset form, leads to a loss of motor skills beginning at 3- to 6-months of age and progresses to blindness, seizures, total incapacitation, and eventual death by 4 years of age. Adult-onset Tay-Sachs is a milder disease with later onset and slower progression. In adults, Tay-Sachs disease 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.
Inheritance: Autosomal recessive.
Cause: HEXA gene pathogenic variants.
Variants Tested: Four pathogenic 7.6kb del, c.1073+1G>A, p.Y427Ifs (c.1274_1277dup TATC), c.1421+1G>C; one mild pathogenic 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, 59 percent in other ethnicities.
Methodology: Polymerase chain reaction (PCR) and fluorescence monitoring.
Analytical Sensitivity and Specificity: Greater than 99 percent.
Limitations: HEXA variants other than those specified above will not be detected. Diagnostic errors can occur due to rare sequence variations.