Defects in beta-galactosidase (GLB1; MIM:611458) can result in GM1 gangliosidosis (GM1; MIM:230500) (Nishimoto et al. 1991) (not described here), with several phenotypes indicating mental deterioration, as well as in mucopolysaccharidosis IVB, a characteristic mucopolysaccharidosis with no neurological symptoms (Callahan 1999).
Mucopolysaccharidosis IVB (MPS IVB, Morquio's syndrome B; MIM:253010) is a rare, autosomal recessive mucopolysaccharide storage disease characterized by intracellular accumulation of keratan sulfate (KS), skeletal dysplasia and corneal clouding. There is no central nervous system involvement, intelligence is normal and there is increased KS excretion in urine (Suzuki et al. "Beta-galactosidase deficiency (beta-galactosidosis): GM1 gangliosidosis and Morquio B disease", p3775-3809 in Stryer et al. 2001). MPSIVB is caused by a defect in betagalactosidase (GLB1), which normally cleaves terminal galactosyl residues from glycosaminoglycans, gangliosides and glycoproteins. The GLB1 gene spans 62.5 kb and contains 16 exons (Oshima et al.1988, Santamaria et al. 2007) and maps to chromosome 3p21.33 (Takano & Yamanouchi 1993).