GLB1 and GM1 gangliosidosis: Monosialotetrahexosylganglioside (GM1) gangliosidosis is an autosomal recessive disorder caused by the lack of ß-galactosidase encoded by GLB1.[1] It is a progressive neurodegenerative disorder, and its manifestations are caused by the accumulation of GM1 ganglioside in the central nervous system.[2] GM1 gangliosidosis is classified into infantile form, late infantile form/juvenile form, and adult form according to the age of symptom onset and severity.