How frequent is Hemophilia in Rh(D) negative individuals?

Haemophilia is a rare condition that affects the blood’s ability to clot. It’s usually inherited. Most people who have it are male. Normally, when you cut yourself, substances in your blood known as clotting factors mix with blood cells called platelets to make your blood sticky and form a clot.

Hemophilia occurs in about 1 of every 5,000 male births.

Although an individual’s haemophilia can usually be traced in the ancestry, in about 30% of cases there is no family history of the disorder, and the condition is speculated to be the result of spontaneous mutation in an ancestor.

There are two main types of haemophilia: haemophilia A, which occurs due to low amounts of clotting factor VIII, and haemophilia B, which occurs due to low levels of clotting factor IX.

Haemophilia A affects about 1 in 5,000–10,000, while haemophilia B affects about 1 in 40,000, males at birth. As haemophilia A and B are both X-linked recessive disorders, females are rarely severely affected. Some females with a nonfunctional gene on one of the X chromosomes may be mildly symptomatic. Haemophilia C occurs equally in both sexes and is mostly found in Ashkenazi Jews. In the 1800s haemophilia B was common within the royal families of Europe.

Haemophilia in European Royalty

Haemophilia C is a mild form of haemophilia affecting both sexes, due to factor XI deficiency. It predominantly occurs in Ashkenazi Jews with an  up to 8% frequency of heterozygosity. Treatment is usually not necessary, except in relation to operations, leading to many of those having the condition not being aware of it.

Studies of gene therapy are in early human trials.