title: Early acceleration of head circumference in children with fragile x syndrome and autism.
abstract: OBJECTIVE
  Head circumference (HC) growth has been shown in several studies to be accelerated early in life in both fragile X syndrome (FXS) and autism spectrum disorders (ASDs), but the rates of growth have not been compared between those with only FXS and those with FXS and ASD (FXS + ASD).
  
  
  METHODS
  We hypothesized that individuals with FXS + ASD would have significantly larger HCs from individuals with only FXS and that there would be an early acceleration of HC in both the FXS-only and FXS + ASD groups. HC measurements were available retrospectively for 44 males, five and younger, with FXS, of whom 22 also had ASD. Measurements over time were available for 24 of the 44 children. HC percentiles were compared between the groups in two ways: by focusing on cross-sectional subsamples and by fitting hierarchical linear models to the full sample.
  
  
  RESULTS
  Neither group differed significantly from the norm in the first year of life (p > 0.2). At 30 months, the FXS + ASD group was 27 percentile points above the norm (p = .0125), whereas the FXS-only group did not differ from the norm. At 60 months, the FXS-only group was 21 percentile points above the norm (p = .029), whereas the FXS + ASD group did not differ from the norm.
  
  
  CONCLUSIONS
  The group difference in HC growth rate may differentiate brain development in individuals with FXS-only versus those with FXS + ASD.
authors.affiliation: Department of Psychiatry and Behavioral Sciences and MIND Institute, University of California Davis, Davis, CA 95817, USA. sufen.chiu@ucdmc.ucdavis.edu
authors.forename: Sufen
authors.initials: S
authors.lastname: Chiu
authors.forename: Jacob A
authors.initials: JA
authors.lastname: Wegelin
authors.forename: Jeremy
authors.initials: J
authors.lastname: Blank
authors.forename: Megan
authors.initials: M
authors.lastname: Jenkins
authors.forename: Josh
authors.initials: J
authors.lastname: Day
authors.forename: David
authors.initials: D
authors.lastname: Hessl
authors.forename: Flora
authors.initials: F
authors.lastname: Tassone
authors.forename: Randi
authors.initials: R
authors.lastname: Hagerman
mesh_terms: D000886:Anthropometry; D001321:Autistic Disorder / Q000453:epidemiology*; D002648:Child; D003430:Cross-Sectional Studies; D005600:Fragile X Syndrome / Q000453:epidemiology*; D006257:Head / Q000254:growth & development*; D006801:Humans; D008297:Male; D012189:Retrospective Studies