Introduction

Haemophilia is a congenital bleeding disorder that affects males. It is estimated that about 400,000 males have Haemophilia A or B.

Patients with haemophilia A have either absent, decreased or defective production of the blood clotting protein, Factor VIII (FVIII). Those with haemophilia B have similar problems with Factor IX (FIX).  Haemophilia is characterised as "severe" when the activity of the affected clotting factor (FVIII or FIX) is less than 1% of normal. Severe Haemophilia is often associated with spontaneous bleeding, i.e. not caused by injury. Haemophilia is termed "mild" when the relevant clotting factor activity is greater than 5%, but less than normal and "moderate" when clotting factor activity is between 1% and 5% of normal.  Approximately 50% of haemophilia patients have severe disease and can require treatment for bleeding several times per month.

Severe haemophilia usually becomes apparent in the first years of life – often as the child starts to move about independently.  Haemorrhages often occur in the joints, particularly knees and ankles. These joint bleeds can cause severe pain and often permanent damage and disability if not treated properly. Other mild, moderate or even life-or-limb threatening bleeds can occur in the muscles, soft tissues, gastrointestinal tract or even the brain.  In addition, trauma, major surgery, tooth extractions or other minor surgical interventions require medical intervention to manage the associated bleeding.

Treatment of haemophilia A and B patients is normally based on replacement therapy, i.e. substitution of the missing clotting factor. The replacement clotting factors are typically obtained from human plasma or, more recently, from recombinant (genetically engineered) preparations.