Mucopolysaccharidosis type II, Hunter syndrome

Mucopolysaccharidosis type II (MPS2) is an X-linked lysosomal storage disorder caused by deficient activity of iduronate-2-sulfatase 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. The heterogeneity of clinical phenotypes, ranging from mild-to-severe forms, is a result of different mutations in the IDS gene. This disorder is characterized by mental retardation, coarse faces, short stature, hearing loss, hydrocephalus, hepatosplenomegaly, dysostosis multiplex, airway obstruction, and cardiac valve disease.