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Foundation Sciences · Genetics

Haemophilia A and B

⏱️ 30 mins read 📖 Genetics 🎯 MLA Relevance: High

Haemophilia A (factor VIII deficiency) and B (factor IX deficiency) are X-linked recessive bleeding disorders presenting with haemarthroses and prolonged bleeding.

📌 Learning Objectives

  • Describe the underlying mechanism of Haemophilia A and B.
  • Identify the key clinical features and complications of Haemophilia A and B.
  • Outline the appropriate investigations and management of Haemophilia A and B.
  • Discuss the implications for patients and families of Haemophilia A and B.
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Curriculum Mapped
UK MLA Curriculum

📋 Overview

Severity correlates with residual factor activity. Diagnosis: prolonged APTT with normal PT, low factor VIII (A) or IX (B) levels.

🔬 Basic Science

Severity correlates with residual factor activity. Diagnosis: prolonged APTT with normal PT, low factor VIII (A) or IX (B) levels.

🏥 Clinical Relevance

Carrier females may have mildly reduced factor levels and can be symptomatic.

🧪 Investigations

Investigation depends on clinical context: relevant blood tests, imaging, and specific genetic or histopathological tests as appropriate. Refer to specialist services where indicated.

💊 Management

Management is condition-specific and typically multidisciplinary, combining medical therapy, surgical intervention where appropriate, supportive care, and family/genetic counselling.

Revision Resources – expand the sections below for high-yield notes, exam pearls, key facts and further reading.

🎯 MLA High-Yield Notes & Quick Revision ⌄
Common SBA themes: recognising the underlying mechanism, identifying classic clinical features, and choosing the first-line investigation or management step. Watch for inheritance pattern and characteristic associations.
haemophilia factor viii factor ix x-linked aptt
  • Haemophilia A is X-linked recessive factor VIII deficiency.
  • Haemophilia B (Christmas disease) is X-linked recessive factor IX deficiency.
  • Both present with prolonged APTT and normal PT.
  • Bleeding into joints (haemarthroses) is characteristic.
  • Recombinant factor replacement and prophylaxis prevent joint damage.
⭐ Exam Pearls ⌄
⭐ High Yield
Haemophilia A is X-linked recessive factor VIII deficiency.
Haemophilia B (Christmas disease) is X-linked recessive factor IX deficiency.
Both present with prolonged APTT and normal PT.
Bleeding into joints (haemarthroses) is characteristic.
Recombinant factor replacement and prophylaxis prevent joint damage.
💡 Clinical Pearl
Haemophilia: Carrier females may have mildly reduced factor levels and can be symptomatic.
⚠️ Exam Tip — Common Mistakes
Confusing the mechanism of Haemophilia A and B with related conditions.
Missing classic clinical features of Haemophilia A and B in SBA stems.
Failing to consider Haemophilia A and B in the differential diagnosis.
🔑 Key Facts ⌄
Haemophilia A is X-linked recessive factor VIII deficiency.
Haemophilia B (Christmas disease) is X-linked recessive factor IX deficiency.
Both present with prolonged APTT and normal PT.
Bleeding into joints (haemarthroses) is characteristic.
Recombinant factor replacement and prophylaxis prevent joint damage.
🔗 Related Topics ⌄
🔬 X-Linked Disorders Foundation Sciences → 📚 Bleeding Disorders 📚 von Willebrand Disease
📚 References ⌄
  1. GMC MLA Content Map
  2. NICE Clinical Knowledge Summaries
  3. BMJ Best Practice

Further Resources

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