This isn’t a typical historical post, but I recently came across a rare medical condition that I thought might interest you. Ulnar dimelia is a congenital deformity where the thumb is absent, the ulna is duplicated, and there are seven or eight fingers in the hand. The condition is often referred to as "mirror hand syndrome.” It is so rare that less than 100 cases have been reported in medical literature - which is why I can’t tell you anything about the history. This is a radiograph of a patient with ulnar dimelia. Swipe to see other images of the hand.