Williams-Beuren syndrome is a rare genetic disease (1/20 000) characterized by a microdeletion at 7q11.23 encompassing about 28 genes, including the elastin gene, ELN. It is a sporadic disease in the majority of cases. Easily identifiable in childhood, this developmental disorder associates suggestive face dysmorphism, cardiac defect, psychomotor retardation and specific behavioural and cognitive profile. We conducted a retrospective study of 11 patients with Williams-Beuren syndrome whose data were collected in the Genetics Department of the Mohammed VI University Hospital of Marrakech. The average age of patients was 6.05 years (SD=6.56; interquartile range=5), with a female predominance (64%; 7/11 patients). Almost all patients were mentally retarded and the diagnosis was confirmed in 100% (11) of patients using fluorescence in situ hybridisation (FISH).

The last decade has seen a growing number of comparative studies on adaptive profiles between individuals with autism spectrum disorder (ASD) and Williams-Beuren syndrome (WBS), showing shared and syndrome-specific adaptive trajectories. Studies have revealed similarities in global adaptive profiles across conditions, while some differences have been found in preschoolers on the specific sub-domains of communication and socialization. However, the majority of studies that have focused on the differences in adaptive functioning across these two conditions used a cross-sectional design. To the best of our knowledge, there are no studies exploring the differences and similarities of adaptive functioning over time.
We compared longitudinal data of adaptive functioning measured by Vineland Adaptive Behavior Scales (VABS) between two samples of children and adolescents with ASD and WBS, matched for chronological age and cognitive/developmental level at the time of the first evaluation.
We did not find any difference on the global adaptive level, both at the first evaluation and over time. However, significant differences emerged on the socialization and communication levels at the time of recruitment. Longitudinal data show that only the socialization domain remains different over time, with individuals with WBS having better functioning than those with ASD. The results on shared and distinct patterns of adaptive functioning between disorders are discussed from a developmental perspective, thus contributing to the implementation of age-specific interventions.