The other weird thing is that there is no common denominator in the dogs that have it. I'm on a yahoo support group and there are people from different countries and the dogs are all different breeds, some purebred, some mutts, big, small, different diets, different environments, etc. Nothing ties these dogs together except the fact that their nails fall off. Some have more pain, some less, some respond to different therapies. There are new people on the list every day. Scary.