Looks like demodetic mange to me...my pup had it when he was around 7mos. and it looked just like that. Didn't seem to itch him tho. My vet said it's common in puppies of that age and usually shows up on face and paws (since it's a mite that is passed from mom to baby when they are nursing...all dogs have this mite). I freaked out when he was diagnosed...but it cleared up fast with a topical ointment the vet gave me and i have not seen it since. He's 14mos. now.
Good luck with the vet! Let us know how he's doing.
prob could have read the last post before posting this! Happy it's not mange!