Hemophilia is a hereditary disease of the circulatory system. Its primary symptom is the total failure of blood clotting mechanisms that can lead to death by exsanguination, even for minor injuries. This disease primarily affects males and is carried on the X chromosome. It requires both parents to be carriers of that defective gene.
However, even if both parents are carriers, the odds of inheriting this disorder is about 25%. In the past affected persons rarely survived childhood, but now the condition can be managed through regular infusions of clotting agents into the bloodstream. Historically hemophilia was referred to as "Royal disease" due to its high occurrence within royal families - Queen Victoria of England (1819-1901) was a famous carrier of hemophilia which she passed down to many European royal houses.