Symptoms of Autism in Males with Fragile X Syndrome: A Comparison to Nonsyndromic ASD Using Current ADI-R Scores

Abstract

Symptoms of autism are frequent in males with fragile X syndrome (FXS), but it is not clear whether symptom profiles differ from those of nonsyndromic ASD. Using individual item scores from the Autism Diagnostic Inventory-Revised (ADI-R), we examined which current symptoms of autism differed in boys with FXS relative to same-aged boys diagnosed with nonsyndromic ASD. In addition, different subsamples of participants were matched on autism diagnostic status and severity of autism symptoms. Between-group comparisons revealed that boys with FXS showed significantly less impairment in Social Smiling than did age-, diagnostic, and severity-matched boys with nonsyndromic ASD. Severity-matched boys with FXS showed more impairment in Complex Mannerisms than did boys with nonsyndromic ASD. Behavioral differences between FXS and nonsyndromic ASD may be of theoretical importance in understanding the causes and correlates of ASD in FXS and in developing and implementing appropriate treatments.

Language Skills of Males with Fragile X Syndrome or Nonsyndromic Autism Spectrum Disorder

“…The samples included in the present study overlap with those of other previously published studies (Benjamin et al 2015; McDuffie et al 2013, 2015; Thurman et al 2015a, b). Consideration for inclusion in the present study required participants with FXS or nonsyndromic ASD to have a nonverbal IQ score less than or equal to 85, as this cut-off is inclusive of essentially all males with FXS (Hessl et al 2009), resulting in the exclusion of 6 children with FXS (3 IQ data not available, 3 IQ scores > 85) and 20 children with nonsyndromic ASD (3 IQ data not available and 17 IQ scores > 85).…”

“…Several publications (e.g., Benjamin et al 2015; McDuffie et al 2013, 2015; Thurman et al 2015a, b) have resulted from this study, but none have addressed the research questions addressed in this paper. Participants were recruited nationally and were assessed at one of two university sites (University of California, Davis and University of Wisconsin, Madison).…”

“…For example, similar weaknesses in pragmatic language, including odd/limited gesture use, difficulties following the rules governing reciprocal communication, atypical rate/intonation, and atypical gaze and facial expressions are seen in boys with FXS+ASD and boys with ASD (e.g., Klusek et al 2014; McDuffie et al 2015). In terms of neurobiology, abnormalities in the GABAergic signaling system have been implicated in both FXS and ASD (Coghlan et al 2012).…”

“…For example, on average, the severity of ASD symptomatology is milder in FXS than in ASD, even for children with FXS who meet diagnostic criteria for ASD (e.g., McDuffie et al 2015; Wolff et al 2012). Moreover, there is evidence to suggest that the developmental trajectory of ASD symptomatology is different in FXS and nonsyndromic ASD (Thurman et al 2015a).…”

Fragile X Syndrome as a Multilevel Model for Understanding Behaviorally Defined Disorders

“…Several researchers have attempted to address this question using behavioral measures. While some have identified similar profiles of autistic traits in both individuals with FXS and those with idiopathic ASD (Bailey et al, 1998), others argue that behavioral profiles are in fact distinct in the two populations (Hall, Lightbody, Hirt, Rezvani, & Reiss, 2010;Kaufmann et al, 2004;McDuffie, Thurman, Hagerman, & Abbeduto, 2014). For example, McDuffie and colleagues (2014) designed a study whereby groups of individuals with idiopathic ASD and individuals with FXS were matched on three different criteria: (1) on chronological age regardless of comorbidity (i.e., some members of the FXS group met and others did not meet the ASD diagnostic criteria); (2) on diagnosis (chronological age matches, taking all the participants with FXS who had received a comorbid ASD diagnosis); and (3) on severity (chronological age together with severity levels of the ASD diagnosis).…”