What is haemophilia?

Haemophilia is a blood clotting disorder in which one of the essential clotting factors is deficient. Haemophilia A, or classical haemophilia, is the most common form, and is due to the deficiency of Factor VIII. Haemophilia B, or Christmas disease, is due to the deficiency of Factor IX.

Haemophilia is hereditary. It affects males almost exclusively, and is passed on through unaffected females who carry the defective gene. However, between one-quarter to one-third of all occurrences appear in families with no previous history of the disorder.

Once haemophilia appears it is then passed on in the same genetic pattern. Approximately one in 6500 males has the disorder. In Australia there are about 1500 males who have haemophilia. The disorder is found in all races and all socioeconomic groups.

There is no cure for haemophilia. It is a lifelong condition. The deficiency of clotting means that people who have haemophilia are vulnerable to episodes of uncontrolled internal bleeding, usually into the muscles or joints. Over a period of time bleeding into joints and muscles can cause permanent damage (such as arthritis in the joints), chronic pain and disability. 

Bleeding episodes, or 'bleeds' may occur spontaneously (apparently without any cause) or as a result of trauma (injury). The bleeding is stopped by infusion of the appropriate clotting factor by intravenous injection.

The common belief that a person with haemophilia gushes blood from cuts and will rapidly bleed to death is a myth. A person with haemophilia bleeds no more profusely than anyone else, just for a longer time.

Minor cuts and scratches pose no problem and require only a dressing and some pressure at the site of bleeding. For deeper cuts, bleeding is simply prolonged because of the failure of the blood to form a tough, adherent clot at the site of damaged blood vessels.

Treatment with clotting factor will then be required.

First signs

With the exception of circumcision, babies seldom have problems before they reach around nine months of age. The first signs of a bleeding problem are likely to occur in early infancy when crawling and walking are first attempted.

These activities will produce the inevitable knocks and twists, which could result in bruises or bleeds into the joints. Painful swelling or a reluctance to use an arm or a leg is an indication that a bleed has occurred. Infant immunisation and other injections should be given subcutaneously.

As children grow, they learn to recognise that bleeding may be occurring. Even before pain or swelling becomes obvious they may recognise a 'funny feeling', which is one of the earliest signs of a joint bleed.

People with haemophilia suffer differing degrees of severity of their disorder. The clinical severity of haemophilia is related to the level of deficiency of the clotting factor.

For people without haemophilia, the normal range of Factor VIII and Factor IX activity varies between 50% and 200%.

Mild haemophilia

People with haemophilia who have a Factor VIII or Factor IX activity of 5% to 25% are classed as mild and usually only experience bleeding problems associated with tooth extractions, surgery or severe accident.

Moderate haemophilia

A Factor VIII or Factor IX activity of 1% to 5% is classified as moderate and haemorrhages are usually related to some injury.

Severe haemophilia

A Factor VIII or Factor IX activity of less than 1% is classified as severe and these people experience frequent and often spontaneous haemorrhages into joints, muscles and tissue. No injury is necessary for bleeding to begin in people with severe haemophilia.

Changes in the frequency of bleeding episodes

Although the degree of severity of haemophilia is lifelong, people with haemophilia tend to experience fewer bleeding episodes in adulthood. The reasons for this are somewhat obscure and may be related to 'self-management' and a mature understanding of the condition.

Treatment

Various treatment products containing the appropriate clotting factor are used to treat haemophilia. These are infused intravenously (as with a blood transfusion) either at the Haemophilia Treatment Centre or at home by parents trained to treat their child, or by the person himself when he is confident enough to do so.

Human immunodeficiency virus and hepatitis

In the 1980s and early 1990s, many of the blood products used to treat haemophilia were infected with the hepatitis viruses and the human immunodeficiency virus (HIV), the virus which causes AIDS.

Thanks to rigorous screening processes and heat treating technology this is no longer an issue in New Zealand. However, universal precautions should always be taken when handling blood, blood products, and equipment, irrespective of their source.

The inheritance of haemophilia

Millions upon millions of cells make up the human body. Each cell has a central nucleus containing 46 chromosomes. The chromosomes contain the genetic information on genes, which determine the individual characteristics of each human being.

Sex discrimination

Two of the 46 chromosomes, called the sex chromosomes, determine the sex of the offspring. Each parent contributes one of these chromosomes to the offspring. The female has two X chromosomes and the male has one X chromosome and one Y chromosome. The sex of any offspring will be determined by any one of four possible combinations of these chromosomes.

Inheritance

Where there is a defective gene on one of the female X chromosomes, haemophilia can be inherited. A female having this defect on a chromosome is called a carrier.

The normal X chromosome carries the genetic information to produce Factor VIII or Factor IX. The defective X chromosome carries little or no such genetic information. No Y chromosome has the genetic information to produce Factor VIII or Factor IX. Hence if the mother's defective X chromosome is linked with the father's Y chromosome, the son will have haemophilia.

When the mother is a carrier and the father is unaffected there will be a 50/50 chance at each birth that the daughter may be a carrier or that the son may have haemophilia.

When the father has haemophilia and the mother is not a carrier, then all their sons will be unaffected and all their daughters will be carriers.

Detection of haemophilia before birth is now possible. Processes such as amniocentesis to determine sex, and fetoscopy and recombinant DNA techniques to identify haemophilia, can be used.

Couples where the prospective mother is, or could be, a carrier have the option of using these new scientific methods. If they wish to do so they are urged to seek advice from the Haemophilia Treatment Centre. Genetic counselling is also available.

von Willebrand's disease

von Willebrand's disease is due to a deficiency of von Willebrand's factor. Deficiency of von Willebrand's factor affects the function of the platelets (a type of blood cell also involved in clotting).

Inheritance

Unlike haemophilia, von Willebrand's disease is not carried on the X or Y sex chromosomes. The gene for von Willebrand's disease can be carried by men or women, and as the gene is dominant, all can show effects of the disorder.

There is a 50/50 chance that each time a child is born to a carrier parent that he or she will inherit von Willebrand's disease. However, the effects will vary from person to person and generation to generation. Unlike haemophilia A and B, brothers, sisters, and parents and be affected with varying degrees of severity.

Original material provided by the Haemophilia Foundation of New Zealand. Reviewed by everybody in March 2005.