Haemophilia is an X linked bleeding diathesis. There are two types – A and B – both due to deficiencies in a plasma protein (Factor VIII and Factor IX respectively) which are key in the coagulation cascade.
Haemophilia is an ideal target for gene therapy as a small increase in the circulating level of FVIII or FIX from 5% of normal, will change the disease phenotype from severe with spontaneous bleeding, to a moderate form in which bleeding is only typically seen after injury/surgery.Â