Related Subjects:
|Iron deficiency Anaemia
|Haemolytic anaemia
|Macrocytic anaemia
|Megaloblastic anaemia
|Microcytic anaemia
|Myelodysplasia
|Myelofibrosis
The most important first step in the management of Essential Thrombocythaemia (ET) 🩸 is to
confirm the diagnosis and exclude other myeloid neoplasms which may mimic ET
(e.g. prefibrotic primary myelofibrosis, masked polycythaemia vera, chronic myeloid leukaemia, refractory anaemia with ring sideroblasts and thrombocytosis).
📖 About
- 📈 Uncontrolled increase in platelet production.
- 🧬 Classified as a myeloproliferative neoplasm (MPN).
- 🤝 Shares features with polycythaemia vera and other MPNs.
- ⚖️ Median survival is >20 years, though risk of complications increases with age.
🧬 Aetiology
- Mutations: JAK2V617F (≈50–60%), CALR (≈20–25%), MPL (≈5–10%).
- Triple-negative ET exists but is rarer and more difficult to diagnose.
📏 Definition / Diagnostic Criteria
- Platelet count ≥450 × 10⁹/L (sustained).
- Presence of JAK2, CALR or MPL mutation.
- If no mutation → must exclude secondary/reactive thrombocytosis.
- Bone marrow: increased mature megakaryocytes in clusters.
🩺 Clinical Features
- 🤕 Microvascular symptoms: headaches, erythromelalgia, visual changes.
- ❤️ Palpitations, dizziness, constitutional symptoms.
- 🩸 Thrombosis → ischaemic stroke, DVT/PE, Budd–Chiari syndrome.
- ⚠️ Paradoxical bleeding (due to acquired vWF defect when platelets >1500 × 10⁹/L).
⚠️ Complications
- Progression to myelofibrosis (10–20% lifetime risk).
- Transformation to acute myeloid leukaemia (AML) (~1–5%).
- Haemorrhage (especially if extreme thrombocytosis).
🧪 Investigations
- Normal CRP and ferritin help exclude reactive causes.
- Platelets often >1000 × 10⁹/L; abnormal giant platelets seen on film.
- Haematinics may be low if chronic bleeding.
- Bone marrow biopsy: increased megakaryocytes, hyperlobulated nuclei.
🔍 Differential of High Platelets
- Acute bleeding or inflammation.
- Iron deficiency anaemia.
- Malignancy, trauma.
- Post-splenectomy reactive thrombocytosis.
💊 Management (per 2018 Algorithm)
- 🧓 Risk stratification: based on age, history of thrombosis, mutation status.
- 🩺 Low risk → aspirin (unless platelets >1500 × 10⁹/L, when bleeding risk ↑).
- 💉 Cytoreduction (hydroxycarbamide 1st line in UK; interferon for young/pregnant; busulfan rarely for older pts).
- 📊 Target platelet count <400–600 × 10⁹/L in high-risk groups.
- 🚫 Avoid aspirin if acquired vWF deficiency present.
📚 References
Cases — Essential Thrombocythaemia (ET)
- Case 1 — Incidental Thrombocytosis:
A 62-year-old woman has a routine FBC for hypertension follow-up. Platelets are 720 ×10⁹/L (persistently elevated), Hb and WCC are normal. She is asymptomatic, no splenomegaly. JAK2 mutation positive. Diagnosis: Essential Thrombocythaemia (low-risk, asymptomatic).
- Case 2 — Thrombotic Complication:
A 55-year-old man presents with sudden onset left-sided weakness. CT confirms an ischaemic stroke. Bloods show platelets 980 ×10⁹/L, Hb 13 g/dL, WCC 9 ×10⁹/L. He has a history of erythromelalgia (burning pain in hands/feet). JAK2 V617F mutation positive. Diagnosis: ET complicated by arterial thrombosis.
- Case 3 — Bleeding in Extreme Thrombocytosis:
A 70-year-old woman presents with recurrent epistaxis and easy bruising. Platelets are 1,600 ×10⁹/L, Hb 12.5 g/dL, WCC 11 ×10⁹/L. Paradoxically, she has an acquired von Willebrand factor deficiency due to very high platelet count. Diagnosis: ET with bleeding complication from acquired vWF deficiency.
Teaching Commentary 🧪
Essential Thrombocythaemia is a myeloproliferative neoplasm characterised by sustained thrombocytosis (>450 ×10⁹/L) due to clonal stem cell proliferation. Most cases are associated with JAK2, CALR, or MPL mutations. Patients may be asymptomatic, or present with arterial/venous thrombosis, microvascular symptoms (erythromelalgia, headaches), or bleeding at very high platelet counts. Management is risk-stratified: low-dose aspirin for most, cytoreduction (e.g., hydroxycarbamide) in high-risk patients (age ≥60, prior thrombosis, platelets >1,500 ×10⁹/L). ET has an indolent course but can transform to myelofibrosis or acute leukaemia.
