Autistic behavior, FMR1 protein, and developmental trajectories in young males with fragile X syndrome.
In fragile X boys, co-occurring autistic behavior—not FMRP level—drives poorer developmental outcomes and slower growth.
01Research in Context
What this study did
The team followed 50 boys with fragile X syndrome from .
They checked each boy every year for autism signs and overall development.
They also measured FMRP, the protein missing in fragile X, to see if low levels hurt growth.
What they found
Boys who showed clear autistic behavior had lower IQ and slower skill gains.
FMRP level made little difference once autism signs were counted.
In plain words: autism features, not the gene problem itself, drove the poor outcomes.
How this fits with other research
Jones et al. (1998) first showed that 1 in 4 fragile X boys score above the autism cutoff.
The new study adds that those same boys also fall further behind each year.
Casey et al. (2009) later found the same pattern in girls: even mild autism signs predicted slower growth.
Together, the three papers build a clear line: fragile X plus autism means watch for slower development.
Why it matters
When you assess a child with fragile X, flag autism features early. Use that flag to plan denser teaching and closer tracking, not just genetic tests.
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02At a glance
03Original abstract
In the context of a longitudinal study, we assessed the relationship between ratings of autistic behavior, FMR1 protein expression (FMRP), and the developmental trajectories of 55 young males with fragile X syndrome. Autistic behavior, as measured by the Childhood Autism Rating Scale, was not related to FMRP expression. However, autistic behavior was a significant predictor of both developmental status and developmental change. Boys with both autistic behavior and fragile X syndrome functioned at significantly lower levels of development and grew at significantly slower rates than those without autistic behavior. FMRP expression accounted for less variance in developmental level than did autistic behavior, and was not significantly related to slope (developmental change over time). No autistic behavior x FMRP interaction was found.
Journal of autism and developmental disorders, 2001 · doi:10.1023/a:1010747131386