NAGLU and mucopolysaccharidosis type 1: Amongst this complex set of diseases, MPSI (Hurler), IIIA and IIIB (Sanfilippo) are inherited neurodegenerative lysosomal storage disorders (LSD) caused by deficiency of the glycosaminoglycan (GAG) degrading enzymes α-iduronidase (IDUA), N-sulphoglucosamine sulphohydrolase (SGSH) or α-N-acetylglucosaminidase (NAGLU) respectively.