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Published on: September 10, 2018
Ten years of enzyme replacement therapy in paediatric onset mucopolysaccharidosis II in England
A Broomfield1, J Davison2, J Roberts1
1Willink Biochemical Genetics Unit, Manchester Centre for Genomic Medicine, St Mary's Hospital, Manchester Foundation Trust, Manchester M13 9WL, UK.
Insights
Enzyme replacement therapy (ERT) in mucopolysaccharidosis II (MPS II) patients significantly improves survival and respiratory function, especially when initiated early. However, ERT shows limited impact on hearing, carpal tunnel syndrome, and cardiac valvular disease progression.
Area of Science:
- Medical Genetics
- Rare Diseases
- Pediatric Endocrinology
Background:
- Mucopolysaccharidosis II (MPS II), also known as Hunter syndrome, is a rare genetic disorder affecting multiple organ systems.
- Enzyme replacement therapy (ERT) has been available for MPS II since 2007, offering a potential treatment avenue.
Purpose of the Study:
- To report the long-term outcomes of pediatric patients with MPS II treated with ERT in England.
- To evaluate the impact of ERT on survival, respiratory function, and other clinical manifestations.
Main Methods:
- Retrospective analysis of 110 patients with pediatric-onset MPS II.
- Comparison of outcomes between patients treated with ERT, untreated patients, and those receiving other interventions (HSCT, intrathecal therapy).
- Assessment of survival, respiratory function (FVC), hearing, carpal tunnel syndrome, and cardiac valvular disease.
Main Results:
- ERT significantly improved survival rates in MPS II patients compared to untreated individuals (median age of death: 15.13 years with ERT vs. 11.43 years without).
- Early ERT initiation (before 8 years) led to better respiratory outcomes at 16 years (median FVC % predicted: 69% vs. 48%).
- ERT had minimal effect on hearing, carpal tunnel syndrome, and cardiac valvular disease progression, which affected 40% of patients.
Conclusions:
- ERT offers a clear survival benefit and improves respiratory function in pediatric MPS II patients, particularly when started early.
- The neurological phenotype in MPS II may be more complex than previously understood.
- Further research is needed to address the limited impact of ERT on certain disease manifestations and to refine management strategies.
Abstract:
The outcome of 110 patients with paediatric onset mucopolysaccharidosis II (MPS II) since the commercial introduction of enzyme replacement therapy (ERT) in England in 2007 is reported. Median length of follow up was 10 years 3 months (range = 1 y 2 m to 18 years 6 month). 78 patients were treated with ERT, 18 had no ERT or disease modifying treatment 7 had haematopoietic stem cell transplant, 4 experimental intrathecal therapy and 3 were lost to follow up. There is clear evidence of improved survival (median age of death of ERT treated (n = 16) = 15.13 years (range = 9.53 to 20.58 y), and untreated (n = 17) = 11.43 y (0.5 to 19.13 y) p = .0005). Early introduction of ERT improved respiratory outcome at 16 years, the median FVC (% predicted) of those in whom ERT initiated <8 years = 69% (range = 34-86%) and 48% (25-108) (p = .045) in those started >8 years. However, ERT appears to have minimal impact on hearing, carpal tunnel syndrome or progression of cardiac valvular disease. Cardiac valvular disease occurred in 18/46 (40%), with progression occurring most frequently in the aortic valve 13/46 (28%). The lack of requirement for neurosurgical intervention in the first 8 years of life suggests that targeted imaging based on clinical symptomology would be safe in this age group after baseline assessments. There is also emerging evidence that the neurological phenotype is more nuanced than the previously recognized dichotomy of severe and attenuated phenotypes in patients presenting in early childhood.
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