genetic conditions are a problem in some dogs, particularly purebreeds. for this reason many of the national kennel clubs require that dogs with certain genetic illnesses or who are deemed to be carriers cannot be registered. some of the most common conditions include hip dysplasia, seen in large breed dogs, von willebrand disease, a disease that affects platelets that is inherited in doberman pinschers, entropion, a curling in of the eyelid seen in shar peis and many other breeds, progressive retinal atrophy, inherited in many breeds, deafness, and epilepsy, known to be inherited in belgian shepherd dogs, german shepherd dogs, cocker spaniels, and st. bernards.