A good friend of ours lost her GSD from DM. One year he was #25 in the world for schutzhund and about 18-24 months later he had to be put down. The DM came into his system quickly and didn't hold back at all. One day he was a little sensitive in his foot and about 8 months later the owner had to put him down. We were all devastated.
The good news is that even a dog with the A/A gene, if bred to a N/N dog the puppies would be, at worst, carriers. If a carrier (N/A) is bred to a N/N dog, then all the dogs will be N/N.
It's sad to see so many GSD breeders refuse to test their dogs, "I don't worry, DM isn't in my lines". How can you tell if you've never tested them?
The test is around $65 (US) and run by OFA - well worth the price. We DM tested our GSD and she's N/N.
