The principal aim of HOS is to collect and disseminate information about the long-term course of Hunter syndrome, especially in patients treated with Elaprase. Participants in this study have been diagnosed with a rare genetic disorder known as Hunter syndrome or Mucopolysaccharidosis Type II (MPS II). This disorder interferes with the body’s ability to break down complex carbohydrates called mucopolysaccharides. HOS (Hunter Outcome Survey) is a long-term observational survey, which examines the medical outcomes of patients with Hunter syndrome (mucopolysaccharidosis II [MPS II]). Patients who do not receive Elaprase or another treatment for Hunter disease during the survey will be followed in order to gain insight into the natural progression of Hunter syndrome.