Laura Ingalls Wilder penned the stories about her family's life as pioneers in Minnesota and Wisconsin. One of the most poignant tales of her youth was about how her older sister Mary went blind as a teenager. The accepted account of her blindness was she had contracted scarlet fever.
But Dr. Beth Tarini, an assistant professor of pediatrics at the University of Michigan, told CNN she spent about 10 years researching exactly what caused Mary to lose her sight. She said she has determined the culprit was not scarlet fever, but viral meningoencephalitis, which causes inflammation of the brain and the meninges, the membrane that covers the brain.
She said she and her team of researchers studied papers and letters Laura wrote, as well as local newspaper accounts of Mary's illness and epidemiological data on blindness and infectious disease during the time period.
Tarini also said she looked closely at Laura's memoir, "Pioneer Girl," and found Mary suffered scarlet fever as a child, but not the year she went blind.
"She never says scarlet fever. She never says rash," Tarini told CNN about Mary's health in the months before she went blind.
The scientist also said Laura had described in letters Mary's condition as "some sort of spinal sickness," while newspaper accounts said she suffered severe headaches.
Tarini told CNN she believes Laura may have changed Mary's condition in her books because she thought scarlet fever would be more relatable to readers at the time.
Tarini's findings were published Monday in the journal Pediatrics.