HEXA and Sandhoff disease: For instance, complex glycosphingolipids are hydrolyzed to glucosylceramides and galactosylceramides through the activity of enzymes such as alpha-galactosidase A (encoded by the GLA gene; that deficiency causes Fabry disease), beta-galactosidase (encoded by GLB1; that deficiency causes GM1 gangliosidosis), sialidases (NEU1, NEU2, NEU3 or NEU4 ; associated to the sialidosis) or beta-hexosaminidase A and B (that deficiencies are associated with mutation in the HEXB gene responsible for Sandhoff disease or with mutation in the HEXA gene responsible for Tay-Sachs disease).