Polycythaemia

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management | References

Definition

Polycythaemia, also known as erythrocytosis, is a condition characterised by an increased concentration of red blood cells in the blood. This can make the blood thicker and less able to travel through blood vessels and organs.

Aetiology

Polycythaemia can be classified into primary and secondary types:

• Primary polycythaemia (Polycythaemia Vera): A myeloproliferative disorder caused by a mutation in the JAK2 gene, leading to overproduction of red blood cells.
• Secondary polycythaemia: Caused by increased erythropoietin production due to chronic hypoxia, tumours, or other underlying conditions.
• Relative polycythaemia: Resulting from decreased plasma volume, often due to dehydration or diuretic use.

Pathophysiology

The pathophysiology of polycythaemia depends on its type:

• Primary polycythaemia (Polycythaemia Vera): Mutation in the JAK2 gene leads to clonal proliferation of red blood cells, increasing blood viscosity and risk of thrombosis.
• Secondary polycythaemia: Increased erythropoietin production in response to hypoxia or inappropriate erythropoietin production by tumours.
• Relative polycythaemia: Reduction in plasma volume without a true increase in red cell mass.

Risk Factors

• Age (more common in older adults)
• Smoking
• Chronic hypoxia (e.g., COPD, sleep apnoea)
• High altitude
• Genetic mutations (e.g., JAK2)
• Use of anabolic steroids or erythropoietin

Signs and Symptoms

Common signs and symptoms include:

• Headache
• Dizziness
• Pruritus (especially after a hot shower)
• Ruddy complexion
• Fatigue
• Splenomegaly
• Visual disturbances
• Thrombosis (e.g., deep vein thrombosis, pulmonary embolism)

Investigations

Specific blood tests and investigations include:

• Full blood count (FBC): Elevated red cell mass, haematocrit (HCT >0.52 in males, >0.48 in females), and haemoglobin levels.
• Erythropoietin (EPO) levels: Low in primary polycythaemia and high in secondary polycythaemia.
• JAK2 mutation testing: Positive in most cases of Polycythaemia Vera.
• Bone marrow biopsy: Hypercellularity with increased red cell precursors in primary polycythaemia.
• Arterial blood gases (ABG): To check for hypoxia in secondary polycythaemia.
• Ultrasound or CT scan: To check for renal or hepatic tumours producing erythropoietin.

Management

Primary Care Management

• Referral to a specialist: Patients with suspected polycythaemia should be referred to a haematologist for further evaluation and management.
• Initial management: Address underlying causes such as smoking cessation, managing COPD, and ensuring adequate hydration.

Specialist Management

• Venesection: Regular removal of blood to reduce red cell mass and haematocrit levels.
• Hydroxycarbamide: Used in Polycythaemia Vera to reduce red cell production.
• Interferon: Another option for reducing red cell production, especially in younger patients or those who are pregnant.
• Low-dose aspirin: To reduce the risk of thrombosis.
• Management of complications: Monitoring and treating thrombotic events, and addressing symptoms such as pruritus.

References

1. NHS. (2024). Erythrocytosis (Polycythaemia). Retrieved from NHS
2. Right Decisions. (2024). Polycythaemia erythrocytosis. Retrieved from Right Decisions
3. BNSSG ICB. (2024). Polycythaemia Guidelines. Retrieved from BNSSG ICB

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