Mucopolysaccharidosis Type I (MPS I) is a lysosomal storage disorder caused by a disfunction of α-L-iduronidase (IDUA), a lysosomal hydrolase coded by the IDUA gene, responsible for degrading two specific glycosaminoglycans (GAGs): heparan sulphate (HS) and dermatan sulphate (DS). The gene discussed is IDUA; the disease is Scheie syndrome.