Leg Pain & Body Twitching in Children: Potential Causes & When to Seek Immediate Care

Question
My son is 5yrs old and has had leg pain for quite a while(growing pains?) he is now experience twitching.  The body twitching has made me very nervous. He does have an appointment with the pediatrician, but the waiting is driving me nuts! Please help explain what this could possibly be.

Answer
He could be having an inflamed nervous system from an immune disorder that is giving the pain. I would probably not wait for the pediatrician but take him to a pediatric emergency room so they can do the tests he needs to find out exactly what type of immune problem it is. OK?