Rate of Chromosomal Anomalies in an Iranian Autism Sample

Background:

Approximately 2% - 5% of individuals with autism spectrum disorder (ASD) have some form of chromosomal abnormality; the most common location is the chromosome 15q11-q13 region.

Objectives:

The rates of chromosomal abnormalities in children with autism have never been examined in an Iranian population. This study examined how rates of chromosomal anomalies in an Iran, where the rate of consanguinity is ~ 20%, compare with those reported for other population samples.

Methods:

Cytogenetic analyses were performed on an unreferred sample of 118 children with ASD enrolled in schools for children with special needs in Iran. These were children with autistic disorder, Asperger syndrome, and PDD-NOS who had no known coexisting genetic condition. ASD diagnoses were made using standard diagnostic tools based on DSM-IV criteria. Cytogenetic analyses were performed using peripheral blood lymphocyte cultures by standard protocols. Fragile X evaluation was done by both polymerase chain reaction and Southern blot.

Results:

Seven of the 118 children with ASD (6%) had some form of chromosomal abnormality; 2 had Fragile X syndrome, 2 had a chromosomal marker of unknown origin, 1 had a fragile site on 1p19, 1 had a fragile site on 1q11, and 1 had a fragile site on 9q11. No evidence of Idic15 or 15q11-q13 anomalies was found. The seven cases with chromosomal anomalies were not significantly different than cases without anomalies on IQ, autism symptoms, parental age, or any other measured variant.

Conclusions:

Our findings are concordant with other reports for overall prevalence of chromosomal abnormalities and fragile sites on the X chromosome in ASD subjects, except that no Idic15 or 15q11-q13 alterations were found. Differences in sample ascertainment across studies may account for this, since some prior studies have examined ASD samples that were specifically referred for cytogenetic examination, while this sample was unreferred.