HEXA and Tay-Sachs disease: Mutations in the genes encoding for α (HEXA), β (HEXB) or GM2-AP (GM2A) proteins affect the lysosomal degradation of GM2 ganglioside and other glycolipids, causing their accumulation into the lysosome and the GM2 gangliosidoses Tay–Sachs (TSD, OMIM #272800), Sandhoff (SD, OMIM #268800), or GM2-activator protein deficiency (AB variant; OMIM #272750), respectively [4].