High-functioning autism spectrum disorder and fragile X syndrome: report of two affected sisters

The methylation status of the mutated FMR1 alleles was examined by Southern blot and methylation-sensitive polymerase chain reaction. The X-chromosome inactivation was determined by analyzing the methylation status of the androgen receptor at Xq12.Both sisters carried a full mutation in the FMR1 gene, with complete methylation and random X chromosome inactivation. We present the phenotype of the two sisters and other family members.These findings suggest that autistic behaviors and cognitive impairment can manifest as independent traits in FXS. Mutations in FMR1, known to cause syndromic autism, may also contribute to the etiology of high-functioning, non-syndromic ASD, particularly in women. Thus, screening for FXS in patients with ASD should not be limited to those with comorbid ID.