- X-linked recessive condition, deficiency of factor VIII, prevalence 1 in 10,000
- Range of possible mutations, 30% of cases due to sporadic mutation
- Low factor VIII levels predispose to bleeding – risk proportional to factor VIII level
- Mild disease (11-30 units/dl) risk after significant trauma/surgery
- Moderate disease (2-10 units) – minor trauma
- Severe disease (<2 units) – frequent, unprovoked bleeds into muscles and joints. May be 30-50 bleeds a year
- Bleeds into joints (haemarthroses) cause chronic deformity, swelling and pain
- Increase in haematuria and intracranial haemorrhage
- Investigations: prolonged APTT, confirmed by factor VIII assay
- Treatment: replacement of factor VIII (self-administered when bleeding occurs)
- 1 unit of factor VIII concentrate contains amount usually found in 1ml of blood
- Spontaneous haemarthroses: correct to 30% normal factor VIII
- More serious bleeds/surgery: 70-100%
- Recombinant therapy preferred to plasma-derived – reducing risk of viral transmission
- Twice weekly prophylactic doses in children reduces bleeds
- May develop inhibitors (antibodies which inhibit factor VIII) – managed with porcine factor VIII, activated factor IX, recombinant factor VIIIa and immune tolerance regimens.
- In mild disease: DDAVP used to mobilise stored factor VIII, antifibrinolytics (tranexamic acid)
- Contraindication for IM injections, avoid NSAIDs (risk of GI haemorrhage)
- Female carriers 10-30% factor VIII – may bleed after trauma.