Mary Ingalls Blindness Not Caused by Scarlet Fever? 'Little House' Sister's Mystery Revealed

Mary Ingalls' blindness was apparently not caused by scarlet fever, as many fans of her sister Laura Ingalls Wilder's "Little House" books previously thought. Television series "Little House on the Prairie" only made Mary Ingalls blindness more known, but it turns out scarlet fever was not the cause.

Mary Ingalls blindness was most likely the result of a brain infection called viral meningoencephalitis, according to Dr. Beth A. Tarini and a team of researchers she assembled. She had read the "Little House" books about Laura and Mary Ingalls' upbringing, and concluded that the 14-year-old could not have been blinded by scarlet fever in 1879.

"When I was a medical student doing my pediatric rotation, I asked my supervising doctor, 'So scarlet fever can make you go blind, right?' and she said no," Dr. Tarini told The New York Times. "I argued- 'Mary Ingalls was a real person. And it said in the book that scarlet fever made her go blind.' But clinically, it didn't make sense."

Dr. Tarini, a pediatrician and researcher at the University of Michigan, enlisted the help of two other doctors, Carrie L. Byington and Jerome I. Finkelstein, to find out why Laura Ingalls Wilder said her sister had scarlet fever.

When she came across Wilders letter and unpublished memoir, the author referred to her sister's illness as "some sort of spinal sickness," but never the world "rash"- the red, splotchy rash is the premier symptom of scarlet fever.

"She never says scarlet fever. She never says rash," Tarini told CNN.

Medical records from the time showed that the few cases of blindness caused by scarlet fever were only temporary. A letter of Wilder's also mentions a Chicago specialist, who said Mary Ingalls' "nerves of her eyes were paralyzed and there was no hope." Furthermore, scarlet fever was often misdiagnosed in the late 1800s.

Evidence pointed to viral meningoencephalitis, which inflames the brain and meninges, and can profess to blindness eventually. Laura Ingalls Wilder could have simply used scarlet fever instead because it was more relatable to her readers.

Tarini's study appeared online Monday in the Pediatrics journal.