 Study TKT024EXT was conducted in 2 phases. The first phase Phase I was 2 years 104 weeks in duration and consisted of weekly infusions of IV idursulfase 0.5 mgkg, and the collection of patients safety and clinical outcomes. Week 105 defined the beginning of the second phase of the study. The second phase Phase II consisted of weekly infusions of IV idursulfase 0.5 mgkg and the monitoring of patients for safety via collection of adverse events, concomitant medications, and vital signs. Study completion was defined as the time a patient either transitioned to commercially available idursulfase or discontinued this study. 