Pathogenic alterations in GLB1 lead to a reduction in affinity for at least one substrate, resulting in either the toxic accumulation of GM1 ganglioside in the nervous system leading to progressive neurological deterioration (GM1 gangliosidosis) or defective storage of galactosyl oligosaccharides and keratin sulfate causing mucopolysaccharidosis type IVB, Morquio type (MIM: 253010) (Regier & Tifft, 2005). The gene discussed is GLB1; the disease is GM1 gangliosidosis.