Approximately 1 in 700-1000 boys are born with an extra X chromosome, also known as Klinefelter syndrome (KS). Because of the risk for development of psychopathology such as autism spectrum disorders, it has been suggested that studying individuals with KS may help in the search for cognitive, neural and genetic mechanisms underlying autism symptoms.
Objectives:
It has remained unclear however, 1) to what extend girls with an extra X chromosome have an increased vulnerability for autism traits and 2) what the profile and severity is of autism traits as compared to children with autism spectrum disorders (ASD). This study will address this.
Methods:
In total, 60 children (35 boys and 25 girls) with an extra X chromosome, 60 boys and girls with ASD and 110 non-clinical controls participated in the study. The age range was 9 to 18 years. We used the Autism Diagnostic Interview-revised (ADI-R) to assess clinical symptoms of ASD. The Social Responsiveness Scale (SRS) and the Autism Questionnaire (AQ) were used to quantify autistic traits.
Results:
Data from the ADI-R showed that 28, 8% of the children with an extra X scored above the cut-off on all three domains: social interactions, communication and rigid or stereotyped behavior. Mean ADI-r scores were similar in boys and girls with an extra X chromosome. In line with this, scores on the SRS and AQ were significantly increased and in between those of controls and children with ASD. The effect size (Cohen’s d) was 1.4, indicating that scores were 1.4 standard deviations higher in the extra X group as compared to the control group. Scores were similar for boys and girls with an extra X.
Conclusions:
Our findings illustrate the profile of increased risk for autism symptoms in children with an extra X chromosome. This may help in diagnosis and treatment of children with an extra X. The absence of gender effects is not only relevant for clinical practice, but may also provide important clues with regard to role of the extra X chromosome in social development. Our findings of elevated levels of autistic traits in both boys and girls with an extra X, stress the relevance of studying X-linked mechanisms.
See more of: Clinical Phenotype
See more of: Symptoms, Diagnosis & Phenotype