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Janus kinase 2
About 🧾
- Janus Kinase 2 (JAK2): A protein tyrosine kinase that mediates cytokine receptor signalling.
- Essential for hematopoiesis, immune regulation, and cell growth.
- Part of the JAK-STAT pathway → transduces signals from cytokines and growth factors.
Aetiology 🧬
- JAK2 Gene: Encodes a cytoplasmic kinase involved in blood cell formation.
- Hematopoietic stem cells: Differentiation into:
- 🩸 Red blood cells (erythrocytes).
- 🛡️ White blood cells (leukocytes).
- 🧩 Platelets (thrombocytes).
Key Mutation: JAK2 V617F ⚡
- Essential Thrombocythaemia (ET): ~50% of cases.
- Polycythaemia Vera (PV): ~95% of cases (diagnostic hallmark).
- Primary Myelofibrosis (PMF): ~50% of cases.
Clinical Relevance 🩺
- Gain-of-function mutation → constitutive activation of JAK-STAT.
- Causes excessive proliferation of blood cells.
- Leads to:
- Thrombosis risk 🧨.
- Splenomegaly ⚖️.
- Progression risk to AML in some patients.
- JAK2 testing = key diagnostic tool in suspected myeloproliferative neoplasms.
Management Implications 💊
- JAK inhibitors (e.g., ruxolitinib) for myelofibrosis and resistant cases.
- Cytoreduction (e.g., hydroxycarbamide) in PV/ET to control counts.
- Aspirin often used in ET and PV for thrombosis prevention (unless contraindicated).
- Ongoing monitoring for:
- Thrombosis / bleeding.
- Progression to acute leukaemia.
- Bone marrow fibrosis.
References 📚
💡 Exam Pearl
Think JAK2 V617F whenever you see: – PV with raised Hb/Hct 🎯 – ET with platelets >450 ×10⁹/L 🧮 – Splenomegaly with constitutional symptoms 🛌
| The content on this website is provided for educational and informational purposes only to support exam preparation (e.g., MLA, MRCP, USMLE) and learning. This is NOT medical advice, diagnosis, treatment, or professional guidance. It does not replace consultation with a qualified healthcare professional, official guidelines (e.g., NICE, GMC, BNF), or supervised clinical practice. Always verify information with current, authoritative sources. Makindo and its contributors accept no liability for any reliance on this content, including errors, omissions, or any resulting harm, loss, or consequences. By using this site, you agree to these terms. |
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