Mucopolysaccharidosis type I (MPS I) (MIM #607015) is a lysosomal storage disorder (LSD) caused by mutations in the gene coding for the lysosomal enzyme α-L-iduronidase (IDUA), one of the lysosomal hydrolases responsible for the degradation of the glycosaminoglycans (GAG) heparan sulfate and dermatan sulfate. The gene discussed is IDUA; the disease is lysosomal storage disease.