I wanted to point out a comment from an adult with primary CMS that was received on the blog earlier...I was glad to read it and know many of you will be too.
I am a perfectly healthy intlligent university student. I have always hand flapped when excited or imagining things, especially as a kid but even now in private as an adult. My parents and siblings never really drew much attention to it...basically accepted it an a unique thing that made me "me". Because of that, I never looked up what might be causing it until today. Primary complex motor stereotypy is definitely what I have.
To any parents out there, if your kid is normal in all other ways don't make a big deal out of it. Kids will realize not to do it in public at some point and automatically regulate it to a private activity. If I had been made to feel "different", I probably would have acted "different". Instead, I have plenty of friends, am doing super well in school and now people just see me as an excitable person.
Also, hand flapping is a very enjoyable thing. Why make children feel guilty for engaging in it?