What is haemophilia?
Haemophilia is an inherited bleeding disorder where the blood doesn't clot properly. It is caused when blood does not have enough clotting factor. A clotting factor factor is a protein in blood that controls bleeding.
- Haemophilia A (also called classical haemophilia) is the most common form, and is caused by having low levels of factor VIII (8)
- Haemophilia B (sometimes called Christmas Disease) is caused by having low levels of factor IX (9).
In Australia there are more than 3,000 people diagnosed with haemophilia, who are mostly male. Severe haemophilia in females is very rare, but some females have lower factor levels and bleeding symptoms. Both males and females with less than 40% of the normal level of clotting factor are now recognised as having haemophilia.
Bleeding is most commonly internal. The low levels of clotting factor produce a wide range of bleeding episodes, usually into the joints or muscles. These bleeding episodes, or 'bleeds', may occur spontaneously, without an obvious cause, or as a result of trauma or injury. Specialised treatment is needed to help blood clot normally and is often infused or injected into a vein. If internal bleeding is not stopped quickly with treatment, it will result in pain and swelling. Over a period of time bleeding into joints and muscles can cause permanent damage such as arthritis, chronic pain and joint damage requiring surgery.
Date last reviewed: 27 August 2021
How is haemophilia passed on?
Haemophilia is an inherited condition and occurs in families; however, in 1/3 of cases it appears in families with no previous history of the disorder. The genetic alteration causing haemophilia is passed down from parent to child through generations.
Read more - can females have haemophilia?
- Men with haemophilia will pass the gene alteration on to their daughters but not their sons.
- Women who carry the gene alteration can pass it on to their sons and daughters.
- Sons with the gene alteration will have haemophilia.
- Most women and girls who carry the gene alteration have normal clotting factor levels. Around 20-30% have reduced clotting factor levels. Sometimes their factor levels are low enought to be classified as having haemophilia, usually mild haemophilia. In a few very rare cases girls and women can have extremely low factor levels and have severe haemophilia.
The diagrams below may assist in understanding inheritance in haemophilia.
- The red males have haemophilia
- The red and blue females carry the gene alteration and some may also have haemophilia. They have one X chromosome with the gene alteration and one unaltered X chromosome.
Date last reviewed: May 2022
Where can I find more information?
For more information and frequently asked questions – click here - Haemophilia FAQ.
Download the HFA information booklets about haemophilia:
Haemophilia - [PDF, 1.7MB]
Living with mild haemophilia: a guide [PDF, 2.9MB]
Click here for other HFA publications on haemophilia.
Australian Bleeding Disorders Registry (ABDR) Annual Report 2019-20. Canberra: National Blood Authority, 2020. [PDF, 2.4MB]
Australian Haemophilia Centre Directors' Organisation. Guidelines for the management of haemophilia in Australia. Canberra: National Blood Authority, 2016.
Hermans C, Kulkarni R. Women with bleeding disorders. Haemophilia. 2018;24(Suppl. 6):29-36.
World Federation of Hemophilia. Guidelines for the management of hemophilia. 3rd edn. Montreal: WFH, 2020.
This resource was reviewed by Leonie Mudge and Kate Lenthen from Australia/New Zealand Haemophilia Social Workers’ and Counsellors’ Group; Anne Jackson, Penny McCarthy, Megan Walsh and Claire Bell from Australian Haemophilia Nurses’ Group; Ian d’Young, Abi Polus and Wendy Poulsen from Australian and New Zealand Physiotherapy Haemophilia Group; Katherine Rose, Senior Genetic Counsellor, Monash Medical Centre, Victoria; Dr Chris Barnes, Dr Simon Brown, Dr Simon McRae and Dr John Rowell from Australian Haemophilia Centre Directors’ Organisation; and bleeding disorder community representatives from HFA Haemophilia and Women’s Project Consumer Review Groups.
Date last reviewed: August 2021
Inheritance and information about women was reviewed by Dr Julie Curtin, Dr Jane Mason and Dr Stephanie P'ng from Australian Haemophilia Centre Directors’ Organisation in October 2018.