title: Evidence of a distinct behavioral phenotype in young boys with fragile X syndrome and autism.
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.
  
  
  METHODS
  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.
authors.affiliation: Carolina Institute for Developmental Disabilities, University of North Carolina at Chapel Hill, NC 27599, USA. jason.wolff@cidd.unc.edu
authors.forename: Jason J
authors.initials: JJ
authors.lastname: Wolff
authors.forename: James W
authors.initials: JW
authors.lastname: Bodfish
authors.forename: Heather C
authors.initials: HC
authors.lastname: Hazlett
authors.forename: Amy A
authors.initials: AA
authors.lastname: Lightbody
authors.forename: Allan L
authors.initials: AL
authors.lastname: Reiss
authors.forename: Joseph
authors.initials: J
authors.lastname: Piven
mesh_terms: D001321:Autistic Disorder / Q000175:diagnosis / Q000235:genetics / Q000523:psychology; D001526:Behavioral Symptoms / Q000175:diagnosis / Q000235:genetics / Q000523:psychology; D002652:Child Behavior; D002675:Child, Preschool; D003937:Diagnosis, Differential; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005149:Facial Expression; D051860:Fragile X Messenger Ribonucleoprotein 1 / Q000235:genetics; D005600:Fragile X Syndrome / Q000175:diagnosis / Q000235:genetics / Q000523:psychology; D006801:Humans; D008297:Male; D015999:Multivariate Analysis; D010641:Phenotype; D011569:Psychiatric Status Rating Scales; D011599:Psychopathology; D012919:Social Behavior; D013239:Stereotyped Behavior
chemical_list: D051860:Fragile X Messenger Ribonucleoprotein 1; C497683:FMR1 protein, human