In 1881 Carl Wernicke described three patients who had delirium, ocular disturbances, and ataxia, but little else in common. One was a seamstress poisoned by sulfuric acid; two were alcoholic men. At autopsy, all were found to have similar brain lesions. Wernicke announced the discovery of a new disease. He called it "hemorrhagic polioencephalitis." Others called it Wernicke's disease, showing what three cases can do for you if you are a well-known German professor.
Six years later a well-known Russian professor, S. S. Korsakoff, also discovered a "new" disease, "psychosis polyneuritica," which became known as Korsakoff's psychosis. It occurred in alcoholics (but not exclusively) and differed from Wernicke's disease in that the course was chronic rather than acute, and was characterized chiefly by amnesia.
The possibility that Wernicke and Korsakoff had discovered the same disease was appreciated by neither. A few years later, Wernicke's assistant, Bonhoeffer, did see a connection.