How do help a child with NPD (Narcissistic Personality Disorder)?

He appreciates nothing, has zero empathy for others, and is starting to exhibit sociopath behaviors and habits, (has been for a number of years now). I have compared his behavior with the symptoms listed in the DSM-IV for NPD, and he exhibits 9 of 9 criteria.

Background:

He is 14, single child in a wealthy home. Adopted and raised by his grandparents (my mom). His biological father was abusive when he was very young, and his biological mother is mentally incapable of raising children, hense the infamily adoption.

He does see a therapist for multiple problems, however they have him diagnosed with ADD, and ODD. While these are legitimate problems, I'm concerned that his primary problem of NPD hasn't been addressed or diagnosed. In fact I find it kind of shocking because he is the worst narcissist I've ever met.

I have little tolerance for his overboard attention seeking behavior, and I always come away from visits feeling infuriated at how disrespectful, self-centered, manipulative, and often abusive he acts towards others. Especially my daughter, whom I often have to take extra time to consul her after visitations at my moms house.

My mom often seeks my advise on parenting issues. Strange, my own mother asking me for advise in these areas. I'm planning on introducing her to the idea that my nephew quite possibly has NPD, (no doubt in my mind). However outside of offering my unprofessional diagnosis, I really don't know what else to tell her, other than bring it up with the therapist. I've googled this topic extensively and it seems to me there is no real practical way to treat or correct NPD, especially in children. Its often overlooked because it's normal for young children to be narcissistic. In short I gather it's not a problem until it is a problem, (if that makes any sense), and its becoming a problem.

My relationship with the boy is odd, he both admires and despises me all at once. I didn't understand this until I recently researched NPD. I think he has a lot of potential if he could only apply himself towards a goal that makes him happy without the requirement of an audience.

I'm looking for any advise from people that have to cope with NPD children. Specifically, how to curb the behavior, as well as how to instill and cultivate genuine empathy towards others.