Identification of expanded alleles of the FMR1 Gene in the CHildhood Autism Risks from Genes and Environment (CHARGE) study.
Order FMR1 CGG-repeat testing for any client who has both autism and developmental delay; six kids in this study had fragile-X expansions that would have been missed without the test.
01Research in Context
What this study did
Flora and colleagues looked for fragile-X gene changes in kids already diagnosed with autism or intellectual disability.
They used a case-control design and ran FMR1 CGG-repeat tests on blood samples.
The goal was to see how many children carried expanded alleles that could cause fragile-X syndrome.
What they found
The lab found expanded FMR1 alleles in six children.
All six kids had both autism spectrum disorder and developmental delay.
The result shows fragile-X changes hide inside some ASD/ID cases.
How this fits with other research
Diemer et al. (2023) later screened 235 Filipino children with ASD and found zero full mutations, but about 6% had intermediate alleles.
The numbers look opposite, yet both papers agree: test for FMR1. Flora saw full expansions in a U.S. sample; C saw none in the Philippines. Geography and sample size explain the gap.
Duerden et al. (2012) argued chromosomal microarray finds more than fragile-X testing alone. Their 24% yield pushed CMA to the front of the genetic line. Flora’s work answers: still add FMR1, because the one case you miss could be the child in front of you today.
Why it matters
You can’t see fragile-X by watching behavior. A quick blood test spots the gene change and guides medical care, family planning, and tailored teaching. Add FMR1 CGG-repeat screening to your referral checklist for every new client who shows both autism and developmental delay. One tube of blood can change a family’s roadmap.
Want CEUs on This Topic?
The ABA Clubhouse has 60+ free CEUs — live every Wednesday. Ethics, supervision & clinical topics.
Join Free →Add one line to your intake form: ‘Medical referral sent for FMR1 fragile-X testing—yes/no.’
02At a glance
03Original abstract
Fragile X syndrome (FXS) is a neuro-developmental disorder characterized by intellectual disabilities and autism spectrum disorders (ASD). Expansion of a CGG trinucleotide repeat (>200 repeats) in the 5'UTR of the fragile X mental retardation gene, is the single most prevalent cause of cognitive disabilities. Several screening studies for FXS, among individuals with ID from different ethnic populations, have indicated that the prevalence of the syndrome varies between 0.5 and 16 %. Because the high co-morbidity with autism, we have conducted a screening study of the cohort from CHARGE, a large-scale, population-based, case control study. We have identified six subjects carrying an expanded allele, which emphasize the importance of screening for FXS in a population with intellectual disabilities and ASD.
Journal of autism and developmental disorders, 2013 · doi:10.1007/s10803-012-1580-2