IDS and mucopolysaccharidosis type 2: Mucopolysaccharidosis II (MPS II; Hunter syndrome; OMIM 309900) is a rare, progressive, X-linked lysosomal storage disease caused by deficient activity of iduronate-2-sulfatase (I2S), which is responsible for the degradation of the glycosaminoglycans (GAGs) dermatan sulfate and heparan sulfate [1, 2].