Beloved British fantasy author Terry Pratchett, author of the Discworld series, was diagnosed last year with early-onset Alzheimer's disease.  The Guardian has a great story on Pratchett, how he's coping, and the news that he has just donated half a million pounds to the Alzheimer's Research Trust.

Pratchett seems in good spirits, however, and finds that one of the biggest problems he has is determining what is a symptom and what is plain old reality for a professional writer:

"When I was going in for the tests, they asked my wife and PA to say what they had noticed in my behaviour. They jointly wrote a letter saying, 'Like any author who's in the throes of writing a book, Terry probably shows all the signs of dementia: he's unworldly, he doesn't pay attention to things, he's antisocial, grumpy.' I'm a typical bloody writer. Maybe all of us have had Alzheimer's for years without realising it.