Mucopolysaccharidosis type IV includes two types depending on the deficient enzyme: galactosamine-6-sulfatase (MPS IVA, type A, Morquio syndrome, OMIM 253000) and beta-galactosidase (MPS IVB, GLB1; 611458, OMIM 253000). The gene discussed is GLB1; the disease is mucopolysaccharidosis type 4.