Pratchett tells fans 'I have Alzheimer's but keep it cheerful'

Terry Pratchett, the bestselling author behind the Discworld fantasy books, has revealed that he is suffering from a rare form of early-onset Alzheimer's while emphasising that he is not dead and would prefer it "if people kept things cheerful".

In a characteristically colourful statement entitled "An embuggerance", the much-loved writer sounded an optimistic note, reassuring his fans that "there's time for at least a few more books yet".

Pratchett said he was taking the news "fairly philosophically ...and possibly with mild optimism".

He added: "Frankly, I would prefer it if people kept things cheerful, because I think there's time for at least a few more books yet."

The 59-year-old, who has sold more than 45 million books worldwide, had consulted doctors after suffering problems with hand-eye coordination which he described as like "wearing typic gloves" while writing. Over the summer the author was told of a "mini-stroke" he had suffered the past few years without being aware of it. Doctors have now diagnosed the Alzheimer's and after consideration Pratchett decided to make the news public.

"I would have liked to keep this one quiet for a little while, but because of upcoming conventions and of course the need to keep my publishers informed, it seems to me unfair to withhold the news," he wrote in a note for the web site of his books' illustrator, Paul Kidby.

Pratchett's fantastical books have been translated into 33 different languages and are followed fanatically by millions of teenage and some older readers the world over. The author has written 36 of the imaginative, humorous novels about Discworld, a flat planet which floats through the universe on the back four elephants which in turn are standing on a giant turtle. Stories are often set in the sprawling, chaotic city of Ankh-Morpork, which dominates the pizza-shaped planet.

The first in the series The Colour of Magic came in 1983, and the books repeatedly topped the best-seller charts thereafter. Making Money, the author's latest completed work which began as a parody of the fantasy genre, was published earlier this year.

Pratchett mastered the divide between children's and adult books before other bestselling authors such as JK Rowling and Philip Pullman followed suit. He has written a number of specifically children's books, including Truckers in 1989, which became the first of its kind to appear in British adult fiction best-seller lists. Two others, The Amazing Maurice and his Educated Rodents won the prestigious Carnegie medal for children's fiction in 2001.

The author, who was awarded an OBE in 1998, has joked: "I am sometimes accused of literature."

Alzheimer's disease, which has no cure and has struck a number of high-profile figures including the novelist Iris Murdoch, affects more than 400,000 Britons and is the most common of more than 100 different types of dementia which get progressively worse.

However, Pratchett spurned sympathy in a post-script to his statement: "I would just like to draw attention to everyone reading the above that this should be interpreted as 'I am not dead'.

"I will, of course, be dead at some future point, as will everybody else. For me, this maybe further off than you think it's too soon to tell.

"I know it's a very human thing to say 'Is there anything I can do?', but in this case I would only entertain offers from very high-end experts in brain chemistry."