An X-linked recessive, hereditary disorder in which abnormally prolonged bleeding recurs episodically at one or a few sites on each occasion

Aetiology

• Haemophilia A - factor VIII deficiency, 5x more common than
• Haemophilia B - factor IX deficiency

Pathophysiology

• No abnormality of primary haemostasis
• Bleeding from medium to large blood vessels, most commonly into joints
• Mild, moderate and severely affected families depending on factor VIII/IX level involved

Clinical features

• Patients with mild haemophilia are usually associated with bleeding only after injury or surgery - diagnosis in this group can often be delayed until quite late in life
• Clinical features of severe haemophilia include:
  • Recurrent haemarthroses
  • Recurrent soft tissue bleeds
    • Bruising in toddlers
  • Prolonged bleeding after dental extractions, surgery, and invasive procedures

Investigations

• Bloods:
  • Isolated prolonged APTT
  • Coagulation factor assays (factor VIII for A, factor IX for B)
• Genetic testing

Management

• The affected clotting factors can be replaced by intravenous infusions - either be prophylactically (for severe haemophilia) or in response to bleeding
  • A complication of this treatment is formation of antibodies  against the clotting factor resulting in the treatment becoming ineffective
    • One-third of boys with severe haemophilia A will develop an inhibitor to factor VIII following factor VIII treatment - treatment of haemophilia with inhibitors should be directed from a specialist centre
• Acute episodes of bleeding or prevention of excessive bleeding during surgical procedures involve:
  • Desmopressin for minor bleeds - stimulates the release of von Willebrand Factor which increases the affected factor sufficiently to deal with the minor bleeding
  • Infusions of the affected factor (VIII or IX) for major bleeds
  • Antifibrinolytics such as tranexamic acid - useful for bleeding wounds but should be avoided in muscle haematomas, haemarthrosis and urinary bleeding as they can lead to fibrosis
• Other supportive management includes vaccination against hepatitis B, hydrotherapy, orthopaedic and dental advice