A recent study confirmed that the different bleeding trends observed amongst patients with haemophilia A is in part associated with the nature of their blood group. The study was presented during the most recent ISTH (International Society on Thrombosis and Haemostasis) Congress, which was held in Melbourne, Australia, from 6 to 10 July 2019, and explored the relationship between the various blood groups (A, B, AB and O) of haemophiliac patients and their ability to produce thrombin, an enzyme that is essential for the formation of blood clots and can only be produced in the presence of factor VIII. The results of the study showed that patients with severe haemophilia and blood group O produce less thrombin than those with haemophilia of an equal severity but a different blood group, i.e. A, B or AB. These results would explain why O group haemophiliacs are, generally speaking, more subject to bleeds, and therefore require more frequent factor VIII transfusions, as demonstrated by previous studies. The researchers who conducted the study postulate that the lower production of thrombin observed in group O haemophiliacs may involve vWF (von Willebrand factor), a small molecule that binds with factor VIII and allows it to perform its function, and that is produced in smaller quantities in these patients than those with other blood groups. More specifically, it has been seen that vWF has multiple functions, including the ability to prolong the half-life of factor VIII, i.e. the time during which it is able to circulate in the blood and contribute to the clotting process before being broken down. The diminished production of vWF in patients with blood group O, is therefore thought to reduce the duration of infusion efficacy, thereby exposing them to a greater risk of bleeds and the need for more frequent infusions.



  • Lott Fonseca F. M. et al, PB0232 – Thrombin Generation in Subjects with Hemophilia A According to the ABO Blood Group. Poster presented during the International Society on Thrombosis and Haemostasis (ISTH) Congress. Melbourne, Australia, 6-10 July 2019. Poster Networking Session. Link: http://www.professionalabstracts.com/isth2019/iplanner/#/grid
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Learn more about the meaning of the words you read on this page and learn about the entire glossary on hemophilia.

A ereditary genetic illness, characterised by a deficiency of clotting factor VIII, that exposes the individual to a greater risk of both internal and external bleeds.

Haemophilia A is more common in males, whereas females tend to be healthy carriers of the condition.

The typical symptoms of the condition include haemarthroses (joint bleeds) and haematomas (muscle bleeds).

Condition that occurs when factor VIII activity is <1%.