The royal disease is hemophilia B, a genetic bleeding disorder that spread through the royal families of Europe after Queen Victoria of England passed the gene to her children in the 1800s. Victoria was a carrier of a mutation that prevents blood from clotting properly, and as her descendants married into the thrones of Britain, Germany, Russia, and Spain, the disease followed them across the continent.
For decades, researchers debated whether Victoria carried hemophilia A or B. A 2009 genetic analysis of bone fragments from the Romanov family settled the question: it was hemophilia B, caused by a mutation in the gene responsible for producing clotting factor IX.
How Hemophilia B Affects the Body
Blood clotting is a chain reaction. When you cut yourself, proteins in your blood activate one another in sequence until a clot forms and stops the bleeding. Factor IX is one of those proteins, and it plays a key role in triggering the final steps that produce a stable clot. In people with hemophilia B, the gene for factor IX is damaged, so the body either makes a shortened, nonfunctional version of the protein or none at all.
The result is that bleeding takes much longer to stop. External wounds are a problem, but the more dangerous issue is internal bleeding, particularly into joints and muscles. Blood can seep into the knees, elbows, and ankles, causing severe pain and, over time, permanent joint damage. In the 19th century, before anyone understood the underlying biology, these episodes were unpredictable and untreatable. Life expectancy for someone with severe hemophilia was under 20 years as recently as the 1960s.
Why It Passed Through Royal Women to Royal Men
The gene for factor IX sits on the X chromosome. Males have one X and one Y chromosome, while females have two X chromosomes. This difference is what made hemophilia so devastating in royal families while remaining largely invisible in the women who carried it.
A male who inherits a damaged factor IX gene on his single X chromosome has no backup copy. He will have hemophilia. A female who inherits the same damaged gene on one X chromosome typically has a normal copy on her other X chromosome, which can produce enough clotting factor to prevent serious symptoms. She becomes a carrier: healthy herself, but capable of passing the mutation to her children.
This pattern meant hemophilia could hide in a family for generations, passing silently through women before suddenly appearing in a son. Each son of a carrier has a 50 percent chance of inheriting the disease. Each daughter has a 50 percent chance of becoming a carrier herself. Victoria had nine children, and at least two of her daughters (Alice and Beatrice) carried the gene, along with her son Leopold, who had the disease. Through their marriages, the mutation entered at least four royal houses.
The Romanovs and the Fall of a Dynasty
The most dramatic political consequence of the royal disease played out in Russia. Victoria’s granddaughter Alexandra married Tsar Nicholas II and became Empress of Russia. Their only son, Tsarevich Alexei, inherited hemophilia B. He suffered repeated bleeding episodes that left him bedridden for weeks. During one crisis, doctors tried every known remedy while the family expected him to die at any moment.
The Romanovs kept Alexei’s condition a strict secret. In Russian culture at the time, any physical defect in a future tsar would be seen as divine judgment, a sign that the family was unfit to rule. Grand Duke Alexander Mikhailovich later wrote that “the Russian people regarded any defect as divine judgment for some sin.” So the royal family withdrew from public life, which only deepened suspicion and resentment among their subjects.
Into this void stepped Grigori Rasputin, a self-styled holy man who appeared able to stop Alexei’s bleeding episodes. Whether through hypnosis, herbal remedies, or sheer coincidence, Rasputin’s apparent healing powers gave him enormous influence over Empress Alexandra. Rumors spread about their relationship, and Rasputin’s presence at court eroded what one historian called the “halo of divine infallibility” surrounding the dynasty. Because the public never knew about Alexei’s illness, they had no framework for understanding why the Empress trusted this controversial figure so completely.
The family’s isolation, the rumors, and the growing public anger all fed into the broader forces that led to the Russian Revolution. When Nicholas II finally abdicated in 1917, he initially planned to pass the throne to Alexei but changed his mind, reportedly saying, “I trust you will understand the feelings of a father.” He abdicated in favor of his brother instead. The entire family was executed the following year.
How the Gene Was Finally Identified
For most of the 20th century, hemophilia A (a deficiency in clotting factor VIII) was the presumed culprit behind the royal disease, simply because it is three to four times more common than hemophilia B. Without genetic evidence, there was no way to confirm which type had plagued Victoria’s descendants.
That changed when researchers analyzed DNA from bone fragments belonging to members of the Romanov family. The results, published in the journal Science, confirmed that Alexei had hemophilia B and that both his mother Alexandra and his sister Anastasia were carriers. Because all documented cases of hemophilia in Victoria’s descendants shared a common genetic origin, this finding settled the question for the entire family line.
The specific mutation occurs in the gene for factor IX on the X chromosome. It disrupts how the gene’s instructions are read by cells, causing the body to produce a truncated, nonfunctional version of the clotting protein.
Living With Hemophilia B Today
The outlook for people with hemophilia B has transformed since the days of the Romanovs. Before clotting factor concentrates became available in the 1960s, severe hemophilia meant a life expectancy under 20. Today, in countries with access to modern treatment, life expectancy has increased dramatically, though it still falls slightly below the general population.
The standard treatment involves infusing clotting factor IX directly into the bloodstream. Early versions of these concentrates were derived from donated human blood plasma, which carried a risk of transmitting bloodborne viruses. Since the 1990s, recombinant factor IX, produced through genetic engineering rather than from human blood, has eliminated that risk.
The most significant recent advance is gene therapy. In 2022, the FDA approved a one-time intravenous treatment for adults with hemophilia B. It uses a modified virus to deliver a working copy of the factor IX gene to liver cells, which then begin producing the clotting protein on their own. For eligible patients, this can reduce or eliminate the need for regular factor infusions.
Hemophilia B remains relatively rare. It is less common than hemophilia A and can be diagnosed through a blood test shortly after birth, or even before birth through prenatal genetic testing. The disease no longer hides in families the way it did in Victoria’s era. Unlike the 19th century royals, who had no way to test for carrier status, modern families with a history of hemophilia can identify carriers and plan accordingly.