IDS and mucopolysaccharidosis type 2: The same approach is being evaluated in MPS II, an X-linked recessive LSD caused by mutations in the iduronate-2-sulfatase (IDS) gene in which patients present in the first years of life with peripheral symptoms manageable with intravenous ERT, but two-thirds also display a progressive and severe CNS involvement (Muenzer et al., 2017).