According to FBI, Al Capone suffered from paresis (a form of neurosyphilis) derived from syphilis.
Following his release, he never publicly returned to Chicago. He had become mentally incapable of returning to gangland politics. In 1946, his physician and a Baltimore psychiatrist, after examination, both concluded Capone then had the mentality of a 12-year-old child.
Capone resided on Palm Island with his wife and immediate family, in a secluded atmosphere, until his death due to a stroke and pneumonia on January 25, 1947.
During America’s Prohibition era, Al Capone headed a Chicago-based crime empire that raked in millions of dollars each year through bootlegging, gambling and other illicit activities. Check out eight surprising facts about the notorious mob boss at History.com.