The lack of β-hexosaminidase activity is related to LSDs: an insufficient functional α-subunit is at the basis of Tay–Sachs disease (OMIM #272800), insufficient function of the β-subunit causes Sandhoff disease (OMIM #268800), and insufficient function of the GM2 activator protein (GM2-AP) originates the AB variant (OMIM #272750) [14]. The gene discussed is GM2A; the disease is Sandhoff disease.