Prader-Willi Syndrome (PWS) is a rare neurodevelopmental disorder stemming from genetic damage in the 15q11-q13 region, leading to hypothalamic dysfunction. Individuals with PWS often exhibit social interaction challenges, intellectual deficits, significant eating disorders, mood disturbances, and sensory-related autistic features. Although PWS is recognized by DSM-5 as a genetic cause of Autism Spectrum Disorder (ASD), ASD diagnosis in PWS remains rare in France. The CASSPER study aims to investigate the distinct autistic and sensory profiles in children with PWS, also analyzing the potential impact of early oxytocin treatment on these manifestations, in line with recommendations for early and tailored intervention.