Mary Ingalls Blindness Caused by Brain Infection, Not Scarlet Fever?

Fans of Laura Ingalls Wilder's "Little House on the Prairie" series know that the author's sister went blind from scarlet fever. But, not so fast, says modern science. A new study suggests that Wilder's older sister Mary likely loster her sight due to viral meningoencephalitis - a disease similar to meningitis.

The study, published in Pediatrics, the official journal of the American Academy of Pediatrics, makes a strong case that Mary was suffering from a brain infection, in which the brain and meninges (the membranes protecting the central nervous system) become inflamed.

The investigation into Ingalls' blindness was sparked by a simple conversation back in medical school, said Dr. Beth Tarini, an assistant professor in the Department of Pediatrics and Communicable Diseases at the University of Michigan in Ann Arbor. According to the "Little House" books, Ingalls went blind in 1879 at 14-years-old because she caught scarlet fever.

"Since I was in medical school, I had wondered about whether scarlet fever could cause blindness because I always remembered Mary's blindness from reading the 'Little House' stories and knew that scarlet fever was once a deadly disease," Tarini said in a press release. "I would ask other doctors, but no one could give me a definitive answer, so I started researching it."

For further evidence, Tarini's team searched through newspaper reports, Wilder's memoirs and letters and even school registries, according to CBS News. The "Little House" heroin wrote in her memoirs her sister Mary was sick with a high fever and "head pains," and had become delirious. She described Ingalls' face as "drawn out of shape," which her mother later explained to her was actually a stroke.

Mary's eyesight diminished as she recovered. "The nerves of her eyes had had the worst of the stroke and were dying, that nothing could be done," a doctor reportedly told the family at the time. 

Researchers also discovered a letter Wilder had written to her daughter, Rose, detailing her sister's "spinal sickness." 

Ingalls' illness was also described in a local newspaper, that explained "it was feared that hemorrhage of the brain had set in (sic) one side of her face became partially paralyzed."

A register from 1889 also listed Mary's cause of blindness as "brain fever" - a term often used to refer to meningoencephalitis at the time. 

"Meningoencephalitis could explain Mary's symptoms, including the inflammation of the facial nerve that left the side of her face temporarily paralyzed and it could also lead to inflammation of the optic nerve that would result in a slow and progressive loss of sight," Tarini explained.

Doctors were able to rule out the possibility of an actual stroke, as there was no evidence of Ingalls having any other paralysis. Bacterial meningoencephalitis wasn't to blame because Ingalls didn't display brain damage and would have had learning problems. But, Wilder wrote that he sister was intelligent even after losing her sight, eventually going to a school for blind children.

Authors of the study hypothesized that editors changed Ingells' illness to scarlet fever because it was rampant around 1840 to 1883 and thus would have been easier to understand. Scarlet fever is caused by an infection of group A Streptococcus bacteria, also responsible for strep throat. The bacteria creates a toxin that causes the red rash, which gives the disease its name. The disease may be curable today, but during "Little House" times it was fatal for 15 to 30 percent of those who caught it and was one of the top four causes of blindness until 1910, authors said.

"Laura's memoirs were transformed into the 'Little House' novels. Perhaps to make the story more understandable to children, the editors may have revised her writings to identify scarlet fever as Mary's illness because it was so familiar to people and so many knew how frightening a scarlet fever diagnosis was," author Sarah S. Allexan, a medical student at the University of Colorado, said in a press release.

Dr. Bruce Hirsch, an infectious disease specialist at North Shore University Hospital in Manhasset, N.Y., told HealthDay he agreed with researchers that Ingalls didn't o blind from scarlet fever, but doubted that she lost her sight due to meningoencephalitis. Instead, he speculated the illness was a viral sickness coupled with a high fever that may have caused her to become dehydrated, which could have caused retinal vein occlusion - a condition where a blood vessel could have blocked a vein supplying the eyes with blood.

"If meningoencephalitis caused enough nerve damage to blind you, it would be unusual for it to just hit that part of the brain without causing a more general injury," he said.

Whatever the cause of the blindness was, Tarini says the study shows that even sicknesses written in books can affect our perceptions of a disease.

"Familiar literary references like these are powerful -- especially when there is some historical truth to them." Tarini says. "This research reminds us that our patients may harbor misconceptions about a diagnosis and that we, as physicians, need to be aware of the power of the words we use - because in the end, illness is seen through the eyes of the patient."