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Comparative Study
. 2012 Dec;51(12):1324-32.
doi: 10.1016/j.jaac.2012.09.001.

Evidence of a distinct behavioral phenotype in young boys with fragile X syndrome and autism

Jason J Wolff  1 , James W Bodfish, Heather C Hazlett, Amy A Lightbody, Allan L Reiss, Joseph Piven
Affiliations
Comparative Study

Evidence of a distinct behavioral phenotype in young boys with fragile X syndrome and autism

Jason J Wolff et al. J Am Acad Child Adolesc Psychiatry. 2012 Dec.

Abstract

Objective: How does the behavioral expression of autism in fragile X syndrome (FXS + Aut) compare with idiopathic autism (iAut)? Although social impairments and restricted, repetitive behaviors are common to these variants of autism, closer examination of these symptom domains may reveal meaningful similarities and differences. To this end, the specific behaviors comprising the social and repetitive behavioral domains in young children with FXS + Aut and iAut were profiled.

Method: Twenty-three male subjects 3 to 5 years old with FXS + Aut were matched by age to a group of 38 boys with iAut. Repetitive behavior was assessed using the Repetitive Behavior Scales-Revised. Social behavior was evaluated using Autism Diagnostic Observation Schedule social item severity scores.

Results: Rates of stereotypy, self-injury, and sameness behaviors did not differ between groups, whereas compulsive and ritual behavior scores were significantly lower for subjects with FXS + Aut compared with those with iAut. Those with FXS + Aut scored significantly lower (less severe) than the iAut group on five Autism Diagnostic Observation Schedule measurements of social behavior: gaze integration, quality of social overtures, social smile, facial expressions, and response to joint attention.

Conclusions: The behavioral phenotype of FXS + Aut and iAut are most similar with respect to lower-order (motoric) restricted, repetitive behaviors and social approach, but differ in more complex forms of restricted, repetitive behaviors and some social response behaviors. These findings highlight the phenotypic heterogeneity of autism overall and its unique presentation in an etiologically distinct condition.

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Conflict of interest statement

Disclosure: Dr. Reiss has served as a consultant for Novartis. Drs. Wolff, Bodfish, Hazlett, Lightbody, and Piven report no biomedical financial interests or potential conflicts of interest.

Figures

Figure 1
Figure 1
Mean and 95% confidence intervals for Repetitive Behavior Scale, Revised (RBS-R) subscale scores for boys with fragile X syndrome and autism (FXS + Aut) and idiopathic autism (iAut). Note: * p < .05, ** p < .01, *** p < .001.
Figure 2
Figure 2
Mean and 95% confidence intervals Autism Diagnostic Observation Schedule (ADOS) social domain scores (social initiation) for boys with fragile X syndrome and autism (FXS + Aut) and idiopathic autism (iAut). Note: JA = Joint Attention; * p < .05, ** p < .01, *** p < .001.
Figure 3
Figure 3
Mean and 95% confidence intervals for Autism Diagnostic Observation Schedule (ADOS) social domain scores (social response) for boys with fragile X syndrome and autism (FXS + Aut) and idiopathic autism (iAut). Note: JA = Joint Attention; * p < .05, ** p < .01, *** p < .001.
Figure 4
Figure 4
Radar graphs of Repetitive Behavior Scale, Revised (RBS-R) subscales and Autism Diagnostic Observation Schedule (ADOS) social initiation and social response items for boys with fragile X syndrome and autism (FXS + Aut), fragile X without autism (FXS w/o Aut), and idiopathic autism (iAut). Note: IJA = Initiated Joint Attention; QoSO = Quality of Social Overtures; RJA = Response to Joint Attention.
See this image and copyright information in PMC

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