Background There is little evidence of the effects of early treatment with growth hormone (GH) in infants with Prader-Willi syndrome (PWS). A prospective study was conducted to assess the safety of GH therapy in infants younger than 2 years of age with PWS. Methods A total of 14 patients with PWS started treatment with GH under the age of 2 years and were followed over a 2-year period. A deletion of chromosome 15 was present in nine infants (64.3%) and maternal uniparental disomy 15 in five infants (35.7%). The median age at start of GH treatment was 9.6 months (interquartile range [IQR] 9.0–18.3 months). Changes in height standard deviation score (SDS), body mass index (BMI) SDS and subcapsular and tricipital skinfolds in the follow-up period were evaluated with a mixed-model regression analysis using the Package R. Results There were no fatal adverse events. A significant decrease (p < 0.001) in tricipital and subcapsular skinfold thickness, with an upward trend of height SDS and a downward trend of BMI SDS, was observed. Infants who started GH before 15 months of age started walking at a median of 18.0 [17.0–19.5] months vs. 36.6 [36.3–37.8] months for those who began treatment with GH after 15 months of age (p = 0.024). Conclusions GH treatment in infants with PWS less than 2 years of age is safe and improved body composition. Infants who received GH before the age of 15 months started to walk earlier.

Angelman syndrome (AS) is a neurogenetic disorder characterized by severe developmental delay with absence of speech, happy disposition, frequent laughter, hyperactivity, stereotypies, ataxia and seizures with specific EEG abnormalities. There is a 10–15% of patients with an AS phenotype whose genetic cause remains unknown (Angelman-like syndrome, AS-like). Whole-exome sequencing (WES) was performed on a cohort of 14 patients with clinical features of AS and no molecular diagnosis. As a result, we identified 10 de novo and 1 X-linked pathogenic/likely pathogenic variants in 10 neurodevelopmental genes (SYNGAP1, VAMP2, TBL1XR1, ASXL3, SATB2, SMARCE1, SPTAN1, KCNQ3, SLC6A1 and LAS1L) and one deleterious de novo variant in a candidate gene (HSF2). Our results highlight the wide genetic heterogeneity in AS-like patients and expands the differential diagnosis.