Christmas disease, also known as hemophilia A, is a rare genetic disorder that affects the body's ability to clot blood. It is named after Prince Leopold, Queen Victoria's youngest son, who suffered from the condition. Prince Leopold was known to bleed easily, even from minor injuries, and was unable to participate in many of the activities that his siblings enjoyed. It's thought that the name Christmas disease came from the fact that hemophilia A is typically diagnosed during the holidays when children are more prone to accidents.