GNS and mucopolysaccharidosis: Mucopolysaccharidoses (MPS) are a group of inherited diseases caused by mutations in genes encoding several lysosomal enzymes (including ARSB, GALNS, GLB1, GNS, GUSB, HGSNAT, HYAL1, IDS, IDUA, NAGLU, and SGSH), which are involved in the degradation of glycosaminoglycans (GAGs).