The risk factors that can favour the appearance of factor VIII inhibitors have for some time now represented the focus of a great many studies, because they represent the ideal starting point for the development of effective prevention strategies. Although subjects with moderate forms of haemophilia may also be exposed to the risk of developing inhibitors, those with severe haemophilia A are undoubtedly more prone to this threat.

Most of the information we currently have on risk factors regards cases in which inhibitors develop within the first 50 days of treatment with replacement therapy. It is, however, possible for inhibitors to appear a long time after the first 50 days of treatment and in some cases they develop years after the start of therapy. It is precisely these cases that form the focus of an on-going study that was recently presented at the 27th ISTH (International Society on Thrombosis and Haemostasis) Congress held last July in Melbourne, Australia. The study, which is being conducted by Dr Amal Abdi, is the result of a joint project involving a number of centres in Holland, Italy, Sweden, Germany and Spain, and aims to identify the presence, in patients with moderate haemophilia A, of risk factors associated with both the patient’s intrinsic characteristics and the type of factor VIII used for the infusions that may facilitate the development of inhibitors beyond the first 50 days of treatment.

The preliminary results of this project, which were presented during the Congress, made it possible to identify certain risk factors, but we will have to wait for the end of the study to find out its conclusions.



  • Abdi A. et al. OC 32.2 – Risk Factors for Inhibitor Development after 50 Exposure Days in Non-severe Hemophilia A – Preliminary Data of a Case-control Study. Abstract from the 27th ISTH Congress and 65th Annual Scientific and Standardization Committee (SSC) Meeting. 6-10 July 2019, Melbourne, Australia
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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 protein belonging to the clotting factor category, a group of enzymes involved in the blood-clotting process.

It is encoded by a gene on the long arm of the X chromosome.

Factor VIII is also known as anti-haemophilic factor (AHF).

Antibodies produced by the immune system of patients with haemophilia, following an infusion of replacement factor VIII.

The inhibitors recognise the infused factor VIII and bind with it in a specific manner, thereby neutralising its effect.