Reading through the posts below I didn't want to argue with anybody, but after consideration I thought it might be reasonable to ask this;

Because somebody believes something does that make it true or do they need treatment?  At what point does a persons belief in something about themselves become a mental illness?

Please take a moment to read a little about this currently described identity disorder.

http://www.nytimes.com/2005/03/22/health/psychology/at-war-with-their-bodies-they-seek-to-sever-limbs.html

Now if after reading this do you think if you had an 8 year old and they thought that one of their limbs didn't belong would you help them remove it or would you seek psychiatric treatment.  Do you think they would suffer their entire lives if they didn't have the limb removed?