I found a great article at CNN about an elderly artist named Frank Calloway, who admits to having just a 3rd grade education, is diagnosed with dementia and schizophrenia and who is still creating at age 112! He has lived in different mental facilities since 1952 and is currently in a nursing home in Alabama. Apparently he is getting a lot of attention and people now want to buy his unique folk art which is sometimes drawn on butcher paper that is 30' long. I may have seen his story on CBS Sunday Morning. It sounds very familiar.
Here's the link to the full story along with a picture of him, some audio and a slideshow with photos of his art. It's a very good read.