I only mention this now because he does eat and drink, so it's not as if he has NO sense of smell. However, I think it is a bit impaired.
For example, there are times when he'll sniff wet food and walk away. I know he's GOT to be hungry, because I measure all their food and they have specific feeding times. So, what I'll do is pop some into his mouth (ok, it's a bit harder to do than just pop the food in there, but you get my point) and THEN he'll gobble it up. It's as if he can't smell it well, but once he tastes it, it's all good.
I know that sense of smell and taste are significantly related (i.e., if he can't smell, he probably can't taste it well either), but I can't think of anything else that would cause him to be this way.
But, I'm more curious than concerned right now, because he DOES eat well and drink.