Combined Intracerebroventricular Enzyme Replacement and Cord Blood Transplantation in Patients with Mucopolysaccharidosis Type II Diagnosed Through Newborn Screening

Enzyme replacement therapy (ERT) for central nervous system symptoms and newborn screening (NBS) is available in Japan for patients with mucopolysaccharidosis type II (MPS II). Of 12 suspected cases identified through the NBS program, 3 patients were diagnosed with neuronopathic MPS II (2 directly from the screened cohort and 1 affected sibling). We reviewed the clinical courses of these patients, who were treated with intracerebroventricular (ICV) ERT using idursulfase beta (Hunterase®) followed by umbilical cord blood transplantation (CBT). Heparan sulfate (HS) in the cerebrospinal fluid (CSF) was longitudinally measured as a therapeutic biomarker, and developmental age was evaluated. All patients achieved successful engraftment with no severe complications, except for one patient with sinusoidal obstruction syndrome. The CSF HS concentration showed a temporary increase during the ERT discontinuation period, which can be attributed to CBT, and a subsequent reduction after the resumption of ICV-ERT. The patients exhibited age-appropriate development. The pattern of change in HS indicates the importance of continuing ICV-ERT even after hematopoietic stem cell transplantation. The study results demonstrate that the combination of ICV-ERT and CBT may yield promising outcomes in patients with neuronopathic MPS II, underscoring the importance of early intervention through NBS.