The risk of developing inhibitors varies throughout the lifetime of a patient with haemophilia, with historical evidence suggesting the majority of inhibitors have developed during childhood, at an average age of 12 years [8]. More recent analysis, however, shows that inhibitor development occurs in children with severe haemophilia at

an average age of 1–2 years after 9–12 treatments [8]. The highest risk of developing inhibitors is observed within the first 50 exposures to FVIII, with the risk reducing substantially after 200 treatment days [8]. The occurrence of inhibitor following administration of FVIII or FIX should be regularly detected using AZD3965 a Bethesda inhibitor assay (BIA) for which detailed description

has been reported elsewhere [10]. Development of inhibitors should also be suspected and investigated, using a BIA, in cases of abnormal response to FVIII or FIX (i.e. poor recovery, shortened duration of effect or inadequate clinical response) [7]. The complex interplay between host genetic factors and circumstances involved with the treatment environment are critical contributory elements to inhibitor development [7,9]. The aim of this study was to discuss the identification Ivacaftor datasheet of patients with haemophilia who may develop inhibitors, and furthermore to highlight the key environmental risk factors for inhibitor formation that may, Interleukin-3 receptor in the future, allow for the prediction and thus the prevention of immune reactions to factor replacement therapy. Non-modifiable patient-related factors that may enhance the risk of inhibitor development include a high-risk haemophilia genotype, co-stimulatory genotype–immunogenotype interactions, ethnicity and positive family history [9,11–13]. Identification of these factors allows for the possible prediction of risk and may also enable modification in treatment to facilitate more targeted therapy. Extensive research has revealed the role of genetics in inhibitor development during FVIII treatment in patients with haemophilia [11,14,15]. Genetic

candidates for predisposing patients to inhibitor development include mutations of FVIII or FIX genes (F8 or F9) [14]. Patients with mutations to their F8 or F9 genes can generally be divided into two types: those with severe molecular defects (termed null mutations as the FVIII or FIX proteins fail completely), including large deletions, nonsense mutations and intron-22 inversions; and patients with milder molecular defects, including missense and splice site mutations, who have loss of function (truncation) but not complete absence of the FVIII or FIX protein [14]. Inhibitor prevalence in patients with null mutations ranges from 21–88% in haemophilia A and 6–60% in haemophilia B, and in patients with missense or splice site mutations, inhibitor prevalence is <10% [14].