�y��vlog

Dr Kernoff's search for suitable subjects led him to Mark Stewart, his brother, and his father, who all had very mild cases of von Willebrand's disease - another type of blood clotting disorder.

"But von Willebrand's disease is the commonest bleeding disorder worldwide and it is equally common among men and women, although women tend to be more symptomatic," she said.

Of an estimated 100,000 victims of clotting disorders in the U.S., 50,000 have hemophilia A and 15,000 have B. Another bleeding disorder that is similar in its effects on patients, but totally different in inheritance and incidence is von Willebrand's disease.

It is given by intravenous drip to victims of hemophilia A and von Willebrand's disease when they have crises of massive bleeding.