​Haemophilia is caused by an X-linked (sex-linked) condition whereby the haemophilia gene is located on the X chromosome. Males carry chromosomes XY and females carry chromosomes XX. When the X chromosome of a male contains the abnormal haemophilia gene mutation, he will have haemophilia. However, if a female carries the haemophilia gene on 1 of her X chromosomes, she is only a carrier and thus will not have the bleeding disorder as the other X chromosome is normal.

A female child will inherit 2 X chromosomes, one from her mother and one from her father (XX). A male child will inherit an X chromosome from his mother and a Y chromosome from his father (XY). This means that fathers cannot pass haemophilia on to their sons but mothers can.

A mother who is a haemophilia carrier has a 50% chance of passing the haemophilia gene to her son and daughter. Her son will have a 50% chance of inheriting the condition while her daughter will have a 50% chance of being a carrier. If a father has haemophilia, his Y chromosome will be passed on to his son while his daughter will inherit the X chromosome with the haemophilia gene. The son will not be affected by the father's haemophilia gene but the daughter will be a carrier. In rare cases where both parents have haemophilia genes, there is a 50% chance that their daughter will have haemophilia.

In about 30% of haemophilia cases, there is no history of haemophilia in the family because it is due to a new or spontaneous mutation¹.

Source: ¹National Hemophilia Foundation

​The signs of haemophilia include being easily bruised without significant injury and having swollen joints or muscles due to bleeding in the joint or muscle after injury. Bleeding can occur even without any noticeable injury. The most severe, but rare, types of bleeding are bleeding in the brain and bleeding in the abdomen. These can be life-threatening or can cause permanent disability especially if there is bleeding in the brain.

Haemophilia can be present even in the foetus as it is an inherited genetic disease. However, bleeding is not usually seen till the child has an injury. Bleeding can sometimes occur at birth especially if the birth process is prolonged or complicated. Children with severe haemophilia may start to have many bruises when they start to crawl and bleeding into the knee joints when they start to walk. The milder forms of haemophilia may only present itself in later childhood or teenage years.

​There is currently no cure for haemophilia.

The treatment is factor replacement therapy in the form of injections into the vein with Factor VIII concentrate for Haemophilia A or Factor IX concentrate for Haemophilia B. Therapy can be given in two ways:

1. Prophylactically (Preventive)
   Factor VIII or Factor IX injections are given on a regular basis (at least once weekly, up to every other day) to prevent bleeding. This is currently recommended for children with severe haemophilia as they are prone to bleeding anytime even if there is no injury.
2. "On demand"
   Factor VIII or Factor IX injections are given whenever there is any suggestion of a bleed. This is usually a bleed into a joint and presents with swelling, increased warmth or pain over the joint.

The dose of Factor VIII or IX concentrate depends on the weight of the child as well as the severity of the bleeding. The medicine must be prescribed by a doctor specialising in haematology. Parents may stock up on the medicine at home so that they can give the injections immediately whenever their child has any bleeding. This medicine is expensive and has to be stored in the refrigerator. Parents will be taught how to administer the injections at home (home therapy).

Children with veins that are difficult to find may have to undergo a surgery to insert a portacath, which facilitates the administering of injections. This device consists of a central venous line (a line inserted into a large vein near the heart) that is connected to a "port" buried underneath the skin on the child's chest. Medicines such as Factor VIII or IX concentrate can then be injected directly into the "port" on their chest and into their vein.

The portacath has to be removed and changed if it is blocked or infected. It generally lasts 2 to 3 years.

In the event where a child has internal bleeding, Factor VIII or IX replacement therapy must be given in the form of injections into the vein as soon as possible. If severe internal bleeding such as bleeding in the brain or abdomen occurs, the child has to go to the hospital immediately. This is an emergency as it may be life-threatening. The child will be given very high doses of Factor VIII or IX concentrate in the hospital and may require close monitoring in the Paediatric Intensive Care Unit.

Inhibitors

Some children may develop inhibitors in the course of haemophilia treatment. Inhibitors are antibodies that bind to Factor VIII or IX. This means that the normal factor replacement therapy is no longer effective. This occurs in approximately 20% to 30% of people with Haemophilia A² and 3% of people with Haemophilia B³ on factor replacement therapy. It can happen as early as the first few days after Factor VIII replacement therapy has started and usually occurs within the first few months. The risk of developing inhibitors is related to the type of haemophilia genetic mutation the child has.

It can be difficult to treat haemophilia in children with inhibitors as they suffer from more severe bleeding and joint problems. For patients with low levels of inhibitors, using higher doses of Factor VIII or IX concentrate may be effective in controlling bleeding. For patients with high levels of inhibitors, they will need other medicines to bypass the pathway to control the bleeding such as Factor Eight Inhibitor Bypassing Activity (FEIBA). However, these medicines are very costly.

Immune Tolerance Induction (ITI) is an immune system "desensitisation" technique used to remove a clotting factor inhibitor. This therapy requires administering high doses of Factor VIII or Factor IX concentrate daily until the inhibitor is no longer detectable. ITI is successful in about 70% of patients with Haemophilia A⁴ but it takes a long time, generally 6 to 12 months, for inhibitors to disappear.

Source: ²American Journal of Hematology, ³British Journal of Haematology, ⁴Journal of Thrombosis and Haemostasis

​Children with haemophilia are advised not to take part in contact sports and avoid injury especially to the abdomen or the head as internal bleeding can be life-threatening. However, they are still encouraged to exercise and keep fit through appropriate exercises such as swimming and non-contact sports such as badminton or table tennis. Exercise helps to strengthen their joints and muscles, helping the child to be less prone to bleeding. Some children are on "prophylactic replacement therapy" (i.e. they receive regular injections of factor concentrates, usually 2 to 3 times a week). They can engage in more vigorous exercises and live a normal lifestyle.

The parents and child are educated on the symptoms and signs of early bleeding so that they can administer treatment with factor concentrate injections immediately to stop the bleeding.

It is important to avoid medicines such as aspirin and warfarin that can worsen bleeding.

Useful Links

• World Federation of Haemophilia
  World Federation of Haemophilia is an international not-for-profit organization that was established in 1963.
• Haemophilia Society of Singapore
  This is the website of the Singapore haemophilia patient support group.

Clinical research is vital to the advancement of medical care. Our doctors are passionate about contributing to the future of child health and medicine not only through clinical practice but also research.

• Ng HJ, Lam J, Koh PL, Ho L, Lim CY, Akhbar Ali M, . . . Tien SL (2015). A comprehensive study of current haemophilia care and outcomes in Singapore. Haemophilia : the official journal of the World Federation of Hemophilia, 21(5):e428-31. doi: 10.1111/hae.12729