Deficiencies of the enzyme β-N-acetylhexosaminidase (Hex) cause rare, autosomal recessive, fatal, neurodegenerative lysosomal storage disorders called GM2 gangliosidoses, including Tay-Sachs disease (TSD) and Sandhoff disease. Hex enzyme is a heterodimer encoded by HEXA (α subunit) and HEXB (β subunit), whose mutations result in TSD and Sandhoff disease, respectively.