Epilepsy is a seizure disorder, where the afflicted person can't stop shaking because of disturbed brain activity.
King Tut ruled Egypt for ten years in the 1300s BC, until he died at 19. His tomb was discovered in 1922.
The researchers studied the boy king's family history, looking for clues as to why he died so young. Their theory hinges on the fact that Tutankhamen had a feminized physique, as did his immediate predecessors (who were his relatives). Paintings and sculptures show these men had unusually large breasts and wide hips, the researchers said, and all of them died quite young.
Study researcher Hutan Ashrafian, a surgeon at Imperial College London, spoke with The Washington Post:
“It’s significant that two [of the five related pharaohs] had stories of religious visions associated with them,” says Ashrafian. People with a form of epilepsy in which seizures begin in the brain’s temporal lobe are known to experience hallucinations and religious visions, particularly after exposure to sunlight. It’s likely that the family of pharaohs had a heritable form of temporal lobe epilepsy, he says.
The disorder would explain a feminized physique (seizures disrupt sex hormones) and his broken leg at the time of his death. There are plenty of other theories about what caused Tutankhamen's death, though, and most likely we will never know.