Mucopolysaccharidosis type I (MPS I) is an autosomal recessive lysosomal disorder which originates from a deficiency in α-L-iduronidase (IDUA), an enzyme required for the proper degradation of two glycosaminoglycans (GAG)—namely, dermatan and heparan sulfate (HS) [88]. The gene discussed is IDUA; the disease is Scheie syndrome.