Thrombocytosis

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

Definition

Thrombocytosis is a condition characterised by an abnormally high platelet count in the blood, typically above 500 x 10⁹/L. It can be classified as primary (essential thrombocythaemia) or secondary (reactive thrombocytosis).

Aetiology

Thrombocytosis can be caused by a variety of factors:

• Primary (essential) thrombocythaemia: A myeloproliferative disorder resulting from genetic mutations (e.g., JAK2, CALR, MPL).
• Secondary (reactive) thrombocytosis: Often due to:
  • Infectious diseases
  • Inflammatory diseases (e.g., rheumatoid arthritis, inflammatory bowel disease)
  • Neoplasms
  • Non-malignant haematological conditions (e.g., acute blood loss, iron deficiency anaemia)
  • Functional and surgical hyposplenism
  • Tissue damage (e.g., recent trauma or surgery)
  • Exercise
  • Reaction to medications (e.g., steroids, adrenalin)
  • Pregnancy
  • Allergic reactions

Pathophysiology

In primary thrombocythaemia, the bone marrow produces too many platelets due to genetic mutations. In secondary thrombocytosis, the elevated platelet count is a reactive process to another condition, such as inflammation or iron deficiency, stimulating increased production of thrombopoietin.

Risk Factors

• Genetic mutations (e.g., JAK2, CALR, MPL)
• Chronic inflammatory diseases
• Infectious diseases
• Iron deficiency
• History of splenectomy
• Certain cancers
• Advanced age

Signs and Symptoms

Common signs and symptoms of thrombocytosis include:

• Headaches
• Dizziness or light-headedness
• Chest pain
• Weakness
• Numbness or tingling in the hands and feet
• Visual disturbances
• Easy bruising or bleeding

Investigations

• Full blood count (FBC)
• Peripheral blood smear
• Bone marrow biopsy and aspiration
• Inflammatory markers (e.g., ESR, CRP)
• Iron studies (serum iron, ferritin, TIBC)
• Imaging studies if malignancy is suspected

Management

Primary Care Management

• Referral to a haematologist: For further evaluation and management
• Management of underlying causes: Addressing the primary condition in reactive thrombocytosis (e.g., treating infections, managing inflammation)
• Monitoring: Regular follow-up with FBC and clinical assessment

Specialist Management

• Cytoreductive therapy: Medications such as hydroxyurea or anagrelide to reduce platelet counts in primary thrombocythaemia
• Aspirin therapy: Low-dose aspirin to reduce the risk of thrombotic events
• Management of complications: Addressing thrombotic or haemorrhagic events as they occur
• Regular follow-up to monitor response to treatment and manage any complications

References

1. North & East Devon Formulary. (2024). Thrombocytosis (High Platelets). Retrieved from Devon Formulary
2. NHS. (2023). Thrombocytosis. Retrieved from NHS
3. British Medical Journal (BMJ). (2022). Thrombocytosis: Diagnosis and Management. Retrieved from BMJ
4. American Society of Hematology (ASH). (2021). Clinical Practice Guidelines: Thrombocytosis. Retrieved from ASH

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