GUSB and GM1 gangliosidosis: The three most commonly diagnosed LSDs are mucopolysaccharidosis type VII (MPSVII, caused by a mutation in the gene encoding beta-glucuronidase), Gaucher disease (GD, caused by a mutation in the gene encoding acid beta-glucosidase) and GM1-gangliosidosis (caused by a mutation in the gene encoding beta-galactosidase-1).