IDS and mucopolysaccharidosis type 2: Over the last few years, enzyme replacement therapy (ERT) with recombinant IDS (idursulfase; Elaprase, Shire Human Genetic Therapies, Cambridge, MA, USA) has been licensed in the United States and the European Union for the treatment of MPS II, and been shown to improve endurance, joint mobility, and lung function, and to potentially be beneficial for many patients with MPS II, especially if started early in the course of the disease [2, 7–9].