Hemophilia B, also known as Christmas disease, is the second most common type of hemophilia. The disease was named after Stephen Christmas, who was the first person diagnosed with the condition in 1952. The disorder was ubiquitous in the royal families of Spain, Germany, and Russia. One of the most famous families with this condition was that of Queen Victoria of England; thus, it is known as the "Royal disease." It is a hereditary hemorrhagic disorder resulting from congenital deficit or scarcity of factor IX, which manifests either spontaneously or after traumatic events.
Alshaikhli A, Rokkam VR. Hemophilia B. 2021 Aug 14. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan–. PMID: 32809627.