He was 3 years old at the time and had fragile X syndrome, considered the leading cause of autism.

Fragile X syndrome is the most common form of inherited mental retardation.

Article: Smart approach to testing needed for fragile X syndrome.

It can also be associated with fragile X syndrome.

You can have fragile X syndrome even if your parents do not have it.

A family history of fragile X syndrome, developmental problems, or intellectual disability may not be present.

Triple X syndrome occurs in around 1 in 1,000 girls.

There is currently no drug treatment that has shown benefit specifically for fragile X syndrome.

Some individuals with fragile X syndrome also meet the diagnostic criteria for autism.

It has also shown promising initial results in the treatment of fragile X syndrome.