… Blank-Slate syndrome

Horrisburg-Veldts Syndrome, or as it was more commonly known, Blank-Slate syndrome was a medical mystery.

It was pretty obvious how it worked. When affected, an individual would be placed into a very suggestive state for a period of time, with their mind essentially checking out. During that time, anything anyone said that could be taken as a means of forming your personality or body would be made fact. It was all encompassing, too.

This led a number of researchers to believe that it may be cause by a release of nanomachines or some similar technology, but nothing had been proven yet. (Thanks for the exposition Paradox!)