In l962, 5-year-old Bob Massie developed uncontrollable bleeding in his left knee, a symptom of his hemophilia A, an inherited clotting disorder. It took thirty transfusions of plasma over the next three months to stop the bleeding. Because the knee joint had swelled and locked into place during that time, Bob was unable to walk for the next seven years. Today, Bob still suffers from painful joint bleeds, but he injects himself with factor VIII, the coagulation protein that his body cannot make. The factor VIII soon controls the bleed.

Hemophilia has left its mark on history. One of the earliest descriptions is in the Talmud, a second century B.C. Jewish document, which reads "If she circumcised her first child and he died, and a second one also died, she must not circumcise her third child." Queen Victoria (1819-1901) passed the hemophilia gene to several of her children, eventually spreading the condition to the royal families of England, Russia, Germany, and Spain. Hemophilia achieved notoriety when factor VIII pooled from blood donations was discovered to transmit HIV in 1985. Ninety percent of people with sever hemophilia who used such pooled factor VIII prior to then have contracted AIDS.

Different forms of hemophilia are caused by abnormalities of different clotting factors, but hemophilia A is by far the most common. Symptoms of the hemophilas includes tendency to hemorrhage severely following minor injuries, frequent nosebleeds, large intramuscular hematomas, and blood in the urine.