title: Expressive morphosyntax in boys with Fragile X syndrome with and without autism spectrum disorder.
abstract: BACKGROUND
  Fragile X syndrome (FXS) is the most common inherited cause of intellectual disability, and the most common single gene disorder associated with autism. Language impairments in this disorder are well documented, but the nature and extent of syntactic impairments are still unclear.
  
  
  OBJECTIVE
  To compare the performance of boys with FXS with and without autism spectrum disorder on measures of verb (VM) and noun (NM) morphosyntax with that of typically developing boys of similar non-verbal mental ages.
  
  
  METHODS
  Conversational samples were obtained from 33 boys with FXS with autism spectrum disorder (FXS-ASD), 35 boys with FXS and no ASD (FXS-O), and 46 typically developing boys (TD). Production of verbal and nominal morphosyntax was assessed separately in these two subdomains. A hierarchical linear model compared morphosyntactic scores in all groups after adjusting for non-verbal cognition, articulatory skill, and caregiver education. The model also tested interactions between group and morphosyntactic subdomain.
  
  
  RESULTS
  Boys with FXS in both groups scored lower than the TD boys on both measures. The FXS-O and the FXS-ASD groups did not differ on either composite measure. All covariates were significantly related to morphosyntactic scores.
  
  
  CONCLUSIONS
  Part of the morphosyntactic impairment in FXS may be attributable to cognitive, environmental, and speech factors. However, it is clear that boys with FXS perform at levels lower than expected from differences in these extra-linguistic factors alone, across both the verb and the noun domains. Clinical interventions should therefore seek to address specific syntactic targets.
authors.affiliation: Psychology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3270, USA. estigarr@email.unc.edu
authors.forename: Bruno
authors.initials: B
authors.lastname: Estigarribia
authors.forename: Joanne Erwick
authors.initials: JE
authors.lastname: Roberts
authors.forename: John
authors.initials: J
authors.lastname: Sideris
authors.forename: Johanna
authors.initials: J
authors.lastname: Price
mesh_terms: D000293:Adolescent; D002648:Child; D002657:Child Development; D002659:Child Development Disorders, Pervasive / Q000150:complications* / Q000523:psychology; D002663:Child Language; D002675:Child, Preschool; D003142:Communication; D005600:Fragile X Syndrome / Q000150:complications* / Q000523:psychology; D006801:Humans; D007804:Language Development; D007805:Language Development Disorders / Q000209:etiology* / Q000523:psychology; D008137:Longitudinal Studies; D008297:Male; D012660:Semantics; D013060:Speech; D014825:Vocabulary