HEXA and Sandhoff disease: Three LSDs associated with GM2-gangliosidosis are Tay-Sachs disease (TSD, OMIM #272800), Sandhoff’s disease (SD, OMIM #268800), and GM2 activator protein deficiency (also called AB variant, OMIM #272750), and are associated with pathogenic variants in HEXA, HEXB, and GM2A, respectively.