Fragile X Foundation Website

I found a website that discusses late speaking in boys due to fragile x syndrome. Fragile X syndrome is the most common cause of autism in children. It affects about 1 in 3600 males and 1 in 5-6000 females, with males typically showing the more severe symptoms in cognitive, physical, and mental development.

Males that have Fragile X will typically have some kind of speech development delay, and is usually one of the first signs that a child may have Fragile X. The amount of speech delay and language complications vary from child to child. Female children tend to not be affected in acquiring language, but may have a problem with conversational skills or pragmatics.

http://www.nfxf.org/html/late-speaking.htm