Inter Individual Variability in Initiation Pathway Activation and Regulation and Phenotypic Heterogeneity in Patients With Haemophilia A and B

Severe haemophilia A and B (SHA, SHB) are X - linked inherited bleeding disorders, characterised by factor VIII and IX levels of \<1 IU/dL respectively. The mainstay of treatment in SHA and SHB is replacement therapy with intravenous infusions of factor VIII and IX. However, there is significant variability in the bleeding phenotype within severe haemophiliacs with some presenting with minimal bleeding episodes even on less intensive treatment regimens. A significant contributor to inter-individual variability in the bleeding phenotype is the coagulation phenotype, but there are no established assays in routine clinical practice that can be used to quantify this. This study aims to study novel assays and characterise the observed phenotypic heterogeneity.