The effect of idursulfase on growth in patients with Hunter syndrome: Data from the Hunter Outcome Survey (HOS)

Hunter syndrome (mucopolysaccharidosis type II) is a rare and life-limiting multisystemic disorder with an X-linked recessive pattern of inheritance. Short stature is a prominent feature of this condition. This analysis aimed to investigate the effects of enzyme replacement therapy with idursulfase on growth in patients enrolled in HOS — the Hunter Outcome Survey which is a multinational observational database. As of Jan 2012, height data before treatment were available for 567 of 740 males followed prospectively after HOS entry. Cross-sectional analysis showed that short stature became apparent after approximately 8years of age; before this, height remained within the normal range. Age-corrected standardized height scores (z-scores) before and after treatment were assessed using piecewise regression model analysis in 133 patients (8–15years of age at treatment start; data available on ≥1 occasion within +/−24months of treatment start; growth hormone-treated patients excluded). Results showed that the slope after treatment (slope=−0.005) was significantly improved compared with before treatment (slope=−0.043) (difference=0.038, p=0.004). Analysis of covariates (age at treatment start, cognitive involvement, presence of puberty at the start of ERT, mutation type, functional classification), showed a significant influence on growth of mutation type (height deficit in terms of z-scores most pronounced in patients with deletions/large rearrangements/nonsense mutations, p