Haemophilia A

Original article by Anthony Rimmer | Last updated on 23/11/2013
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  • 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.