While many medical conditions are well known and easy to diagnose, others remain total mysteries. Some cases might seem mundane at first, only to end up baffling doctors and other medical professionals for decades, if not centuries.
From waking up one day with a foreign accent to remaining trapped in the body and mind of a toddler even as a person ages, these weird, unexplained conditions are a reminder of how difficult it can be to fully understand how the human body works. And sometimes what we do learn is disturbing - especially when there is no known cure.
We present a dozen rare medical conditions that have challenged and baffled the medical world.