Von Willebrand's, von WIHL uh brandz, disease is a hereditary disease in which the skin bleeds for an abnormally long period of time when injured. It is similar to the blood disorder hemophilia (see Hemophilia). However, unlike hemophilia, von Willebrand's disease causes prolonged external bleeding, and internal bleeding is rare. In addition, most hemophiliacs are males, but von Willebrand's disease affects both sexes. Von Willebrand's disease occurs worldwide, but it is most common in the Scandinavian countries. It was first described in 1926 by Erik von Willebrand, a German professor of medicine.