difficult child 2 was tested for fragile x a little over a year ago (?). He is an Aspie, has anxiety disorder, not otherwise specified, pragmatic language disorder, and looks much younger than his chronological age of almost 17 years. Physically, he could easily pass for a 10 - 12 yr old. He is very small for his age both in height and weight. At the time the test was done, he showed absolutely no signs of puberty.
The test came back negative. He is followed by both a developmental pedi and a pedi endocrinologist. After consulting with both of difficult child 2's specialists, we decided to wait a little longer before giving him any sort of growth hormones. Within the last 6 months, he has begun to show a few signs of puberty. He has also gained some height too even though he is still small for his age. This has happened without any medical intervention.
From what I know, you don't have to have fragile x to be on the autistic spectrum. However, I agree with Marg - If you suspect it, it is worth having your child tested. WFEN