Mary Lincoln has been a mystery for more than 150 years. Irritable as the wife of Abraham Lincoln in Illinois, erratic as First Lady, and frankly psychotic as a widow, she died at the young age of 63 after years of unusual physical symptoms and progressively increasing weakness. John Sotos, formerly Adjunct Professor of Medicine at the University of North Carolina, who is now Worldwide Medical Director at Intel Corporation, has solved the mystery in a new article published in Perspectives in Biology and Medicine (Volume 58, Issue 4). Sotos' article "What an Affliction" pinpoints pernicious anemia as the root of Mary's poor health during most of her adult life, and as the cause of her death. Pernicious anemia a type of Vitamin B-12 deficiency.