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What are Inherited Bleeding Disorders? Information from the Queensland Haemophilia centre

Bleeding disorders occur when proteins are missing from the blood, preventing the the normal blood clotting process to occur. In most cases the deficiency is genetic meaning that the person was born with the deficiency and will have it for the rest of his or her life. They may also pass it onto their children.

The most common types of inherited bleeding disorders are von Willebrand's disorder, Haemophilia A (a deficiency of Factor VIII) and Haemophilia B (a deficiency of Factor IX), also known as Christmas Disease.

Deficiencies of other clotting factors as well as abnormalities of platelet function can also cause bleeding disorders.

The severity of the bleeding disorder can vary from mild to severe but remains constant for a particular person during their lifetime and is also usually constant within a family. People with mild bleeding disorders may be unaware that they are affected until they undergo surgery or suffer some trauma. Although these conditions are not at present curable, effective treatment is available.

Inheritance of Haemophilia

Every person has two sex chromosomes. Women have two X-chromosomes while a man has one X and one Y chromosome. Both factor VIII and IX proteins are located on the X chromosome. A fault in the Factor VIII or IX gene on the X chromosome will result in Haemophilia A or B in males because there is not a normal X chromosome to balance the abnormality. In females carrying the haemophilia gene, the normal X chromosome compensates for the abnormal X chromosome.

An affected male cannot pass the disorder on to his sons but all his daughters will carry the haemophilia gene. Sons of women with the haemophilia gene have a one in two chance of being affected and daughters will have a one in two chance of carrying the haemophilia gene.

Chart on inheritance of haemophilia
Reproduced with thanks from Haemophilia Foundation Australia - "Finding out about carrying the haemophilia gene".

Last updated: 23 March 2010