GLB1 and mucopolysaccharidosis type 4: Mucopolysaccharidosis IV (MPS IV, also known as Morquio syndrome; Fig. 8) presents as two genetically distinct disorders, each with a different enzyme deficiency: MPS IVA (Morquio A syndrome; OMIM #253000) due to deficiency of N-acetylgalactosamine-6-sulfatase (GALNS gene), resulting in accumulation of keratan-sulphate (KS) and CS [26, 27]; and MPS IVB (Morquio B syndrome; OMIM #253010) due to deficiency of beta-galactosidase activity leading to urine KS and oligosaccharide excretion as in GM1 patients.