If you’re a fan of the Little House on the Prairie book, you may recall that author Laura Ingalls Wilder’s real-life sister Mary allegedly went blind from scarlet fever at age 14. But although Mary Ingalls did indeed suffer from scarlet fever as a kid, and it can be a cause of blindness for some patients, physicians believe that wasn't the case with Mary. Dr. Beth Tarini and her team discovered a letter written to Laura's daughter in 1937 that mentioned Mary's blindness. But it also mentioned that Mary had "some sort of spinal sickness." Turns out, a doctor at the time inspected the nerves in Mary's eyes and they were paralyzed. As Dr. Tarini dove deeper into the medical mystery, she found the articles from the local newspaper that said in Mary's teenage years she suffered severe headaches and partial paralysis on one side of her face. The researchers came to a conclusion that it wasn't scarlet fever that caused Mary's blindness, but viral meningoencephalitis. The disease inflames the brain and spinal cord and can cause blindness in the optic nerves.