In the Victorian period, the British Royal family was known to carry haemophilia, leading to the condition also being known as ‘the royal disease’. Now, no members of the British royal family are believed to carry the genetic variation that causes haemophilia due to its inheritance pattern.
Haemophilia is a rare condition that prevents blood from clotting. It is caused by a genetic mutation that causes the body to produce fewer clotting factors – substances in the blood that combine with platelets to form clots. As a result, people affected by the condition are likely to bleed for longer periods. There are two main types of the condition with each affecting different clotting factors. Type A prevents normal production of factor VIII, and type B affects factor IX. However, the symptoms of both types are similar.
Queen Victoria is thought to have developed haemophilia B due to a spontaneous genetic mutation. She is believed to have passed it on to several of her children, including her son Prince Leopold, who may have passed away as a result of the condition. Queen Victoria’s daughters, Princess Alice and Princess Beatrice, are also believed to have inherited the genetic variant and spread it to several other royal houses, including those in Russia, Germany, and Spain.
Haemophilia’s inheritance pattern means that it mainly affects males. The genetic mutation that causes it occurs on the X chromosome. Females have two X chromosomes, while males have one X chromosome inherited from their mother and one Y chromosome from their father. This means that females are less likely to develop the condition because even if they inherit one copy of the gene variant, their second X chromosome is very likely to have a normally functioning copy of the gene that can produce clotting factors. In comparison, since men only have one X chromosome and therefore one copy of the gene, if they inherit the haemophilia variant it will be expressed.
This means that not every child with a haemophiliac parent will inherit the condition. Mothers who carry one healthy gene and one altered gene have a 50% chance of passing the altered gene on to their children of both sexes. Fathers with haemophilia will always pass the condition on to their daughters (who inherit their X chromosome), but never to their sons (who inherit their Y chromosome).