Since Birthmarks.com deals with PWS, take a look at this:
They have a better example for PWS treatment.
Also, don't give up until you know that your insurance company has actually denied the claim. Is there someone at the company that you can speak with directly to find out what you have to do?
Is there another physician in your area that you could see? A doc who comes off as rude and uncaring isn't being "honest." Just rude and uncaring. Also, the staff of a physician's office is usually good at knowing how to deal with insurance issues, so they should be helping you.