title: Prevalence of the fragile X anomaly amongst autistic twins and singletons.
abstract: Early screening studies of autistic individuals suggested that up to one-quarter of cases were associated with the Fragile X anomaly. Recent studies find that the usual behavioural phenotype of the Fragile X anomaly is distinct from autism as usually defined, and that a variety of methodological factors contribute to the variability of the prevalence estimates. We report the prevalence of the Fragile X anomaly, using strict cytogenetic criteria, in a large sample of autistic individuals whose diagnosis was confirmed using a standardised diagnostic instrument. The anomaly was detected in 1.6% of tested autistic individuals from a combined sample of: autistic twins; clinic attenders; and, individuals from families multiplex for autism or related cognitive phenotypes. The anomaly was not detected in greater than 2.5% of any of the constituent samples and accounted for only a small proportion of the genetic influences amongst concordant twins and multiplex families. The anomaly was detected in 5% of the 40 tested autistic females, confirming reports that the prevalence of the anomaly is similar amongst autistic individuals of both sexes.
authors.affiliation: MRC Child Psychiatry Unit, Institute of Psychiatry, London, U.K.
authors.forename: A
authors.initials: A
authors.lastname: Bailey
authors.forename: P
authors.initials: P
authors.lastname: Bolton
authors.forename: L
authors.initials: L
authors.lastname: Butler
authors.forename: A
authors.initials: A
authors.lastname: Le Couteur
authors.forename: M
authors.initials: M
authors.lastname: Murphy
authors.forename: S
authors.initials: S
authors.lastname: Scott
authors.forename: T
authors.initials: T
authors.lastname: Webb
authors.forename: M
authors.initials: M
authors.lastname: Rutter
mesh_terms: D000328:Adult; D001321:Autistic Disorder / Q000150:complications* / Q000175:diagnosis / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D002869:Chromosome Aberrations; D003071:Cognition; D015897:Comorbidity; D004200:Diseases in Twins / Q000453:epidemiology* / Q000235:genetics; D005260:Female; D005600:Fragile X Syndrome / Q000175:diagnosis / Q000453:epidemiology* / Q000235:genetics; D006801:Humans; D007223:Infant; D008607:Intellectual Disability / Q000150:complications / Q000453:epidemiology / Q000235:genetics; D007361:Intelligence Tests; D007398:Interpersonal Relations; D007621:Karyotyping; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012737:Sex Factors