From what I understand they can be treated. You may want to email a rescue - specifically
www.puppymillrescue.com they may be able to help you out with info. on treatment etc. There was two little Yorkies last year on petfinder that had dem (oh hell I can't spell. LOL) mange and they were coming around and up for adoption. I think once the pup is in a loving home and under a vet's care it will work wonders.
Elaine