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Myeloproliferative neoplasms (PV, ET, myelofibrosis, CML)
A high count "without a reason" of red cells, platelets or white cells suggests a myeloproliferative neoplasm; PV and ET are linked to a JAK2 mutation (and ET also to CALR or MPL), CML is defined by BCR-ABL, and treatment is aimed at preventing thrombosis: phlebotomy with a haematocrit target below 45% and aspirin.
Why it matters in the exam
The question presents a man with high haemoglobin, itching after a hot shower, facial redness, an enlarged spleen or thrombosis in the hepatic veins (Budd-Chiari). The first step is to separate primary from secondary polycythaemia: in PV, EPO is low and JAK2 V617F is present; in secondary polycythaemia (smoking, sleep apnoea, lung disease, kidney tumours, testosterone) EPO is normal or high. In PV phlebotomy is done to a haematocrit below 45% and aspirin is given; at high risk — age 60 or more or past thrombosis — hydroxyurea is added.
In ET platelets are 450,000 or more, and reactive thrombocytosis is always excluded first (iron deficiency, inflammation, infection, after splenectomy). Very high platelets (over a million) can paradoxically cause bleeding (acquired von Willebrand). CML: leukocytosis with all stages of maturation, basophils and a large spleen; t(9;22) and BCR-ABL, treated orally with imatinib or other tyrosine kinase inhibitors — with near-normal survival. Myelofibrosis: a massive spleen, "teardrop" cells on the film, a "dry tap" on marrow aspiration; ruxolitinib for symptoms, and marrow transplantation is the only curative treatment.
Key points
- PV: JAK2 V617F, low EPO; phlebotomy to haematocrit below 45% + aspirin.
- High risk (age 60 or more or thrombosis): hydroxyurea.
- ET: platelets 450,000 or more, exclude a reactive cause.
- CML: BCR-ABL, t(9;22); imatinib.
- Myelofibrosis: teardrop cells, dry tap, massive spleen; ruxolitinib.
Summary table
| Disease | Clue | Test | Treatment |
|---|---|---|---|
| PV | High haemoglobin, itch after a shower, spleen, thrombosis | JAK2 V617F, low EPO | Phlebotomy to haematocrit below 45% + aspirin |
| High-risk PV | Age 60 or more or past thrombosis | — | Add hydroxyurea |
| ET | Platelets 450,000 or more | JAK2, CALR or MPL; exclude a reactive cause | Aspirin; hydroxyurea at high risk |
| CML | Leukocytosis, basophils, spleen | t(9;22), BCR-ABL | Imatinib (a tyrosine kinase inhibitor) |
| Myelofibrosis | Massive spleen, teardrop cells, dry tap | Marrow biopsy | Ruxolitinib; transplant cures |
| Secondary polycythaemia | Smoking, sleep apnoea, lung, kidney | Normal or high EPO | Treat the cause |
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Sources
- WHO Classification of Haematolymphoid Tumours, 5th edition (2022) — Myeloproliferative neoplasms
- ELN Recommendations for the Management of Philadelphia-negative MPN, 2018 — Risk groups, hematocrit target, cytoreduction
- Harrison's Principles of Internal Medicine, 21st edition (2022) — Polycythemia Vera and Other Myeloproliferative Neoplasms; Chronic Myeloid Leukemia
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-02. The text may contain errors; when in doubt, check the source.