GM1 gangliosidosis (GM1) is a rare, progressive neurodegenerative lysosomal storage disorder caused by biallelic variants in GLB1 encoding β-galactosidase, an enzyme that catabolizes GM1 ganglioside.1 Because neurons have a high content of GM1 ganglioside, the clinical manifestations of GM1 largely involve the central nervous system (CNS). The gene discussed is GLB1; the disease is GM1 gangliosidosis.