IDS and mucopolysaccharidosis type 2: Mucopolysaccharidosis type II (MPS II, also known as Hunter syndrome) is an X-linked lysosomal storage disease caused by the disturbed enzymatic activity of iduronate 2-sulfatase (EC 3.1.6.13), a lysosomal enzyme involved in the degradation of glycosaminoglycans (GAGs) [134].