Autism is defined by impairments in reciprocal social interaction (SOC), communication (COM) and repetitive/restrictive interests and behaviors (RBI). Of late, there has been a suggestion in the literature that components of the ASD phenotype are dissociable and that each may be attributed to differing etiological, neuropsychological, and neurobiological underpinnings. In a parallel line of investigation, there has been an increased interest in characterizing ASD symptom profiles (or rates of comorbid ASD) in individuals with different genetic syndromes associated with intellectual disability. Examining symptom profiles across disorders of known genetic etiology may elucidate mechanisms contributing to the development and fractionation of the ASD phenotype.
We sought to examine ASD symptom profiles using the Social Communication Questionnaire – Revised, Lifetime Version (SCQ) in males with four chromosomal aneuploidies associated with intellectual deficits (XXXY, XXXY, XXXXY, Down syndrome [DS]) and to compare these profiles to that found for a clinically-ascertained group of children with idiopathic ASD.
Ninety-six males, ages 4-30 years, participated (ASD:n=38, XXYY:n=28, XXXY:n=7, XXXXY:n=14, DS:n=9). The mean age of the sample was 11.60±5.65 and the mean verbal IQ was 71.26±14.54. Participants were a subset of individuals enrolled in studies at the NIMH, Children’s National Medical Center, and University of Colorado Medical School.
For data analyses, SCQ total scores were compared among four groups (ASD, XXYY, DS, and a combined XXXY/XXXXY group). Next, the proportion of autism-positive responses on SCQ items in each subdomain (SOC,COM,RBI) was calculated (i.e., # autism-positive responses/# of items in subdomain). This was done so that subdomain scores which include different numbers of items could be compared directly.
SCQ total and subdomain scores were examined non-parametrically using Kruskal-Wallis tests. For SCQ total and subdomain scores, there were significant effects of group (all X2s>12, all ps<.01). Follow-up Mann-Whitney tests revealed that the ASD group had greater SCQ total scores than the combined XXXY/XXXXY and DS groups (ps<.05 Bonferroni-corrected), but not the XXYY group. For the subdomain scores, the pattern was SOC: ASD>XXXY/XXXXY,DS; COM: ASD>all groups; RBI: ASD>XXXY/XXXXY,XXYY. To examine disorder-specific profiles, within-group subdomain comparisons were completed utilizing Friedman tests. No significant differences between subdomain scores were detected within the XXYY, XXXY/XXXXY, and ASD groups. Rather, SCQ profiles were flat. For the DS group, SOC was marginally less impaired than both COM and RBI (p<.05 uncorrected).
This research contributes to the growing literature on ASD profiles in genetic disorders. The pattern of findings varied when examining SCQ total versus subdomain scores. The ASD group was more impaired than the combined XXXY/XXXXY group for all scores. In contrast, the ASD group had greater COM and RBI symptom endorsement scores than the XXYY group, but did not differ on total and SOC scores. Finally, the ASD group was more impaired than the DS group on all scores except RBI. This research suggests that examining SCQ subdomains may be more informative when characterizing ASD symptomatology in children with genetic disorders. Additionally, studying these subdomains in groups with distinct genetic syndromes may elucidate mechanisms underlying the fractionable ASD phenotype.
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