If you have a child with juvenile arthritis and Down's syndrome, which one would be more likely to get cancer? I would think that that since juvenile arthritis is an auto-immune disease, it would be more likely to happen in that case than a child with Down's syndrome. This was a discussion in class and some of us feel we were right. I tried finding information on any website, but am not having any luck. Does anyone have a website that would have this info? Thanks.