"Merlin Sickness" is the term used to describe the strange condition afflicting Rachel Weintraub after her encounter with the Shrike on Hyperion, which causes her to age backward.
Symptoms[]
While not a disease in the conventional sense, the symptoms of Merlin Sickness are a physiological reversal of the aging process, accompanied by a sequential erasing of the victim's memories. With each passing day, the victim will appear one day younger than they were before, and an entire day's worth of memories will be lost. The end result is that the victim's physical and mental age regresses until they return to a stage of infancy, after which they will presumably die.