Hemophilia

Haemophilia or hemophilia is the name of any of several hereditary genetic illnesses that impair the body's ability to heal bleeding wounds. Genetic deficiencies cause lowered plasma clotting factor activity so as to compromise blood-clotting; when a blood vessel is injured, a scab will not form and the vessel can continue to bleed excessively for a very long period of time. The bleeding can be external, if the skin is broken by a scrape, cut or abrasion, or it can be internal.

Table of contents

1 Treatment
2 Causes
3 History
4 See also

Treatment

Haemophilia can be controlled quite successfully today by regular injections of a given clotting factor such as Factor VIII.

Causes

Haemophilia is generally caused by a mutation affecting the genes encoding one of the clotting factors. These genes are located on the so-called X chromosome, so haemophilia is a sex-linked trait.

Women have two X-chromosomes whereas men have one X and one Y-Chromosome. Since the mutations causing the disease are recessive, a woman carrying the defect on one of her X-chromosomes will not be affected by it, as the equivalent allele on her other chromosome would express itself to produce the necessary clotting factors. However the Y-chromosome in men has no gene for factors VIII or IX. If the gene responsible for blood clotting on a man's X-chromosome is deficient there is no equivalent on the Y-chromosome, so the deficient gene is not masked by the dominant allele and he will develop the illness.

Since a man receives his single X-chromosome from his mother, the son of a healthy woman silently carrying the deficient gene will have a 50% chance of inheriting that gene from her and with it the disease. By contrast, for a woman to inherit the disease, she must receive two deficient X-chromosomes, one from her mother and the other from her father (who must therefore be a haemophiliac himself). Hence haemophilia is far more common among men than women. However, haemophiliac daughters are more common than they once were, as improved treatment for haemophilia means that more men survive to adulthood and become parents. Adult women with haemophilia menstruate periodically, so they must take clotting factor to survive.

(As with all genetic disorders, it is of course also possible for a person to acquire it fresh, rather than inheriting it, because of a new mutation in one of his or her parents' gametes.)

History

Haemophilia figured prominently in the history of European royalty. Queen Victoria passed the mutation to her son Leopold and, through several of her daughters, to various royals across the continent, including the royal families of Spain and Russia. For this reason it was once popularly called "the royal disease." (The British and German monarchs descended from Victoria did not inherit the mutation.)

The diseases were passed on to:

Princess Alice, who passed it onto:
- Irene, who passed it onto two of her three sons: Waldemar and Henry
- Friedrich
- Alexandra, who passed onto her only son, Alexei
- (It does not appear that Princess Alice's oldest daughter Victoria, maternal grandmother to Prince Philip, inherited the mutation; if she had there would be a danger of him reintroducing the disease to the British royal family.)
Prince Leopold, who passed it onto Alice, who in term passed it onto one of her two sons, Rupert.
Princess Beatrice, who passed it onto three of her four children:
- Victoria Eugenie, who passed it onto Alfonso (Prince of the Asturias) and Infante Gonzalo.
- Leopold
- Maurice