Should people with myotonic dystrophy lift weights?

I was diagnosed with myotonic dystrophy when I was 24. At the time it didn't affect me too much apart from a little bit of weakness in my hands. Now I am 31 and I am beginning to notice the symptoms becoming a little bit worse. I actually work as a fitness instructor and have tried to find out information about the best exercise to do to prevent muscle wasting but it seems that most people who have this condition don't do anything! Some sources actually advised people NOT to lift weights. I have always believed that exercise done in the right way can help any medical condition so I thought that perhaps body building training might help? My doctors have been pretty useless on giving me advice, I don't think they know very much about it. I saw a specialist who told me to try it and see what happens. Not very helpful. Anybody out there got any information to help? I don't want to end up looking like a skeleton in a few years!