Mary Todd Lincoln had a lot of tragedy in her life. She lost two young children -- and, of course, was sitting next to President Lincoln when he was assassinated.
All of that contributed to years of depression, but now a medical expert believes there was a physical cause for her mental struggles.
History has not been kind to the wife of our 16th president. She was known to be a tempestuous, unpredictable force, and her son eventually had her committed. Sally Field's 2012 portrayal of Mary Todd showed a fierce and sharp-tongued first lady.
"You think I'm ignorant of what you're up to because you haven't discussed this scheme with me as you ought to have done," she said in one scene. "When have I ever been so easily bamboozled?"
But Dr. John Sotos, a physician and medical historian, says the famously fiery first lady was not only misunderstood - but misdiagnosed. Sotos puts forth a new theory about Mary Todd Lincoln -- her erratic behavior was caused by a condition called pernicious anemia.
"Pernicious anemia is an autoimmune disease that starts in the stomach and that impairs the body's ability to absorb food efficiently," Sotos said. "And as a result, the person becomes B12 deficient eventually, and that causes lots of problems in every organ of the body."
It was a fatal illness until treatment was discovered decades after her death. The disease can lead to many of the symptoms exhibited by Mary Todd Lincoln: a sore mouth, pale skin, difficulty walking and psychiatric problems. It can also cause swelling.
"The puffiness is not in a way that would occur with just an accumulation of fat," Sotos said.
Today, the disease can be picked up on a simple blood test and easily treated with B12 supplements.
"She had a sick brain and was doing the best that she could in a very complicated, relentlessly demanding environment," Sotos said. "And I think to have done as well as she did with the kind of handicaps that she had, I think that deserves admiration."