Just because somebody calls you names like ret*d doesn't mean they're telling the truth. My son is called a moron, ret*d, etc, and he has a very high IQ. People with asperger's syndrome are often misunderstood by others, that's why we get called names, not because the names are true. According to what I've read DiGeorge syndrome doesn't cause people to be ret*d, although in general the IQ is on the low end of normal... which is to say, not ret*d. It can cause certain learning difficulties, but learning difficulties don't mean someone is ret*d, just that they have a different mental make up.
I also have dyscalculia, dyspraxia, schizoaffective disorder... and was diagnosed autistic when I was little, considered to have asperger's syndrome now. When I've had IQ tests my scores have been scattered between very high, and actually ret*d. (I got sixty in one of the mathematical tests. One hundred was normal, so now you know how bad my maths is!) IQ tests really don't matter that much. The fact is that you can read, write, communicate with people, express your thoughts and feelings. So don't worry if people call you names. They're idiots.
My son is also on the asperger's spectrum. His IQ levels out at the genius range, but his dyspraxia, dyscalculia and social anxiety are such that he often just freezes and can't communicate very well. This doesn't mean he's ret*d (though he's been called that) It just means that he struggles in certain situations.
You'll probably find a cluster of symptoms that we tend to share. Thank you for asking an interesting question.