HEXB and Tay-Sachs disease: Disabling mutations in HEXA, HEXB or the gene encoding for GM2AP results in Tay-Sachs disease (TSD; OMIM #272800), Sandhoff disease (SD; OMIM #268800) or the less common AB variant (OMIM #272750), respectively, a subset of lysosomal storage disorders (LSDs) collectively referred to as GM2 gangliosidosis.4