Originally Posted by Ariana:
Sounds to me like possibly high functioning autism or Aspbergers. I had a child who had similar "quirks". The parents did not see it at all and I slowly went insane trying to figure it all out! In the end I was 100% sure it was Aspbergers. From what I have read kids do not usually get diagnosed with Aspbergers until later in life because they tend to slip by unnoticed for the most part, meaning people just think they are "quirky" or "odd" but not in a way that hinders them too much. Girls are even harder to diagnose because they tend to figure out how to be social.
Have you completed an MCHAT? Maybe start there and see how things go? Although I am not sure there is one for this age group.
The MCHAT is only for use with kiddos between 18-30 months. It's a checklist to catch kids early. The new ASQ:SE has autism "red flags" built into their screening.
OP mentions a few things that stand out as red flags for ASD concerns. (Rigidity, difficulty with eye contact) There aren't so many that I'd be super concerned, unless there are other things.
Temperament and his intelligence could be playing a role here. Sometimes kids who really bright have interests that don't align with their peers. It makes it challenging for them to make friends.
Getting the parents perspective would also be a good in this situation. Are they concerned? If so, go from there. A good place to start with finding resources would be the local school district for an evaluation or the pediatrician.