Mucopolysaccharidosis type I (MPS1) is an autosomal recessive lysosomal storage disorder caused by deficient activity of alpha-L-iduronidase in glycosaminoglycan degradation. The enzyme defect results in the accumulation of heparan sulfate and dermatan sulfate in many organs, as well as elevated metabolite levels in urine. Hurler syndrome is characterized by coarse faces, hydrocephalus, dysostosis multiplex, cardiac valve disease, airway obstruction, and mental retardation. Scheie syndrome is a milder form.
