I know a child who may have Fragile X syndrome? Has anyone experienced this & what are the long term effects?

I have done a lot of research about it and have found out that it occurs mainly in boys. The little boy I know is developmentally and physically slow for his age. He did not start walking until around 18 months. (He is know a little over 2 years old) He has a very limited vocabulary. My child is the same age as him, but there is a big difference between their level of comprehension and understanding. I am in the medical field and have not heard of this syndrome until know. You can do all the research that you want but they don't really give you what the long term effects are? I am really hoping to hear from someone who has a child with this syndrome or someone who know someone who has a child with this syndrome.