I know I'm going to seem a bit dumb here, but I'd never heard of SM before I joined this site. I have had Maddy since October & she appears to be very healthy. She's about 3 years old & was picked up by the pound . I wasn't looking for any breed in particular, I just wanted a cat friendly dog. Now obviously I have no background on her & so don't know which breeder she came from etc... She was in good shape when she was found & is very well trained so someone cared for her. My point is, how would I know if she had/got it? what are the symptoms? & does it affect dogs when they reach a certain age? I love her so much & whatever happens to her in the future I would gladly care for her. I'm just a little concerned. Judy x ps. I didn't see the TV programme on the BBC everyone is talking about.