The development or worsening of scoliosis during GH treatment is a concern, even considered a contraindication by some clinicians. Scoliosis is commonly found in children with Prader-Willi syndrome (PWS), occurring in 30% <10 yrs and 80% >10 yrs of age (vs. 2.7% in controls). The hypotonia in PWS patients is likely a major pathogenic factor, associated with so-called “long C-curve scoliosis” seen in children with neuromuscular disorders. Since GH treatment may improve muscle strength, it is unclear whether GH treatment is detrimental or might even improve scoliosis in patients with PWS. The aim of this Dutch study was to determine the rate of onset and progression of scoliosis. Prepubertal children (n=82) were studied in a randomized, controlled trial over 2 years, while the smaller number of pubertal patients (n=9) were studied at two different GH doses. At baseline, overall 36% of patients had scoliosis (defined as >10 degree curve on x-ray): 29% in infants, 36% of prepubertal, and 67% of pubertal PWS patients. After 2 years, there was no difference in the onset of scoliosis in GH treated vs controls (22% vs. 33%, respectively; OR = 0.42) or progression of scoliosis (3.3 vs. -5.0 degrees, respectively, p = 0.27). In addition, there was no correlation between features that one might expect to be associated with a risk of onset or progression of scoliosis, such as delta height SDS or IGF-1 SDS. As one might predict, delta trunk lean body mass (LBM) was associated with a tendency for regression of scoliosis, but only during the first year of the study. The investigators conclude that scoliosis should not be considered a contraindication for scoliosis in children with PWS. They do recommend yearly spine x-rays. The findings from this trial are reassuring and provide important guidelines for pediatric endocrinologists treating PWS children. Steve LaFranchi, MD