Prader-Willi syndrome (PWS) is caused by either the structural loss of material or the absence of gene expression from the paternally inherited copy of chromosome 15 (q11-q13). In addition to a well-described behavioral phenotype that includes hyperphagia, obsessive-compulsive symptoms, disruptive behavior, cognitive delays, research also suggests that some persons with PWS have repetitive behavior and social deficits reminiscent of autism spectrum disorders (ASD). In particular, it appears as though those individuals with the maternal uniparental disomy (m-UPD) subtype of PWS are at greater risk for autistic symptomatology than those with paternal deletions (DEL) of 15q11-q13. These findings are particularly intriguing in light of data implicating maternal duplications of the same chromosomal interval in idiopathic autism, as well as evidence that functional alterations of genes in this region are associated with social deficits found in a variety of neurodevelopmental disorders.
The primary objective of this research is to examine social functioning in individuals with PWS and to further test the hypothesis that m-UPD is a specific risk factor for autistic symptomatology.
42 individuals with PWS (23 DEL, 19 m-UPD) and 19 individuals with an ASD (7-36 years old) and their caregivers comprised the total sample. Participants underwent intelligence testing (WISC-IV, WAIS-III, or WASI), adaptive functioning (Vineland Adaptive Behavior Scales), and the Autism Diagnostic Observation Schedule (ADOS). Parents completed the Autism Diagnostic Inventory-R (ADI-R), as well as the Social Competence Inventory (SCI; Rydell, 1997) and Social Responsiveness Scale (SRS; Constantino & Gruber, 2005).
For social responsiveness, SRS-Total score significantly differed between ASD, m-UPD, and DEL groups (F = 7.275, p =.002; controlling for age and IQ). Post-hoc comparisons indicate significantly more social difficulties were present for participants with ASD and m-UPD than those with DEL. 78.9% of m-UPD and 36.4% of DEL participants scored in the highest clinically significant range indicating severe interference in everyday social interactions. Groups also differed significantly on measures of social competence. Participants with m-UPD and ASD evidenced greater impairment in the SCI Prosocial Orientation Subscale (e.g., empathy, understanding of others, helpfulness) than those with DEL (F=7.2, p=.002 controlling for age and IQ). No differences were found between groups on the Social Initiative Subscale [DEL = 3.04(.82), m-UPD = 2.64(.72), ASD = 2.51(.72)]. Among those with PWS, the SRS-Total score and SCI Prosocial Orientation was significantly negatively correlated with Vineland Social Subscale.
These findings indicate individuals with PWS have difficulty initiating social interaction (e.g., making contact with unfamiliar peers) and may be prone to social hesitancy or withdrawal similar to those with an ASD. Prosocial behaviors such as generosity, empathy, and helpfulness were more evident in those with DEL subtype than in individuals with m-UPD or ASD. Results will be discussed in relation to ADOS and ADI-R findings. These results give further insight into the social functioning of persons with PWS and indicate need for social-skills intervention in this population.
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