IDUA and mucopolysaccharidosis type 1: Mucopolysaccharidosis type I is caused by a deficiency of the glycosidase alpha-L-iduronidase (α-L-iduronidase iduronohydrolase, EC 3.2.1.76; IDUA) and the resulting accumulation of undergraded dermatan sulfate and heparan sulfate [1].