This forum is for questions and support regarding
Down Syndrome issues such as Dental Problems, Communication Problems, Developmental Disabilities, Hearing Loss, Hypothyroidism, Immune System Problems, Learning Disabilities, Joint Problems, Muscle Weakness, Respiratory Disorders, Seizures, Sleep Apnea, Weight Problems.
Also, Angelman Syndrome is something to look into, and I couldn't find a helpful link for you. It seems the ones i found were impossibly difficult to navigate. I used to know a child with Angelman's, and she sounds a lot like your son.
Best wishes in your quest. I hope you find answers soon.
http://www3.interscience.wiley.com/cgi-bin/abstract/116330609/ABSTRACT