GLB1 and mucopolysaccharidosis type 4A: Mucopolysaccharidosis type IV (Morquio syndrome) is determined by impairment of the enzymes galactosamine-6-sulfate sulfatase (GALNS) (MPS IVA OMIM#253000) or beta-galactosidase 1 (GLB1) (MPS IVB OMIM#253010), which are involved in the breakdown of keratan sulfate and chondroitin sulfate.