He may be A "Red Legged Yorkie". I don't know much about it, you can read more about it here on YT. But from what I understand they are yorkies but they don't really grow hair, and if they do its wiry. I read that their litter mates may look like normal yorkies too, so maybe that's what he is. I could be wrong though.....
Here is a thread about one:
http://www.yorkietalk.com/forums/gen...rkie-zack.html