Abraham Lincoln was the tallest U.S. President at 6 feet 4. Besides being exceptionally tall, Abraham Lincoln had unusually long limbs and digits. These extraordinary proportions drove modern scientists to believe that Lincoln could have had Marfan syndrome. This syndrome is a relatively rare genetic condition that prevents the connective tissue in a human body from “gluing” cells together. Marfan syndrome cannot be cured but it is possible to treat the symptoms allowing for a normal life span.