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When I visited Ricaurte, Colombia, in 2016, I was surrounded by men with long faces and prominent ears. As we spoke, they would ask repetitive questions while mumbling and failing to maintain eye contact, and when they shook my hand, they turned their body away from me. They were interested in me but were too shy to interact. This type of anxiety-related approach-withdrawal behavior is typical of those with fragile X syndrome (FXS), a well-characterized genetic disease that is the most common inherited form of intellectual disability and the most common single-gene cause of autism. Even many of the Ricaurte women, who usually have at least one good copy of the X chromosome, showed similar social deficits. I had never seen so many individuals with FXS all together. I thought to myself: This is ground zero for FXS.
Likely because the ...
