The JAK2 V617F mutation is present in the majority of patients with polycythaemia vera (PV). According to ELN 2018 criteria, a diagnosis of PV requires which major criterion in addition to bone marrow findings?
- A JAK2 V617F positivity alone regardless of haemoglobin
- B Haemoglobin >16.5 g/dL in men or >16.0 g/dL in women (or haematocrit >49%/>48%) ✓
- C Splenomegaly on imaging
- D Erythropoietin level below normal
Correct answer: B. Haemoglobin >16.5 g/dL in men or >16.0 g/dL in women (or haematocrit >49%/>48%)
Explanation
WHO 2022/ELN criteria for PV include: Major criterion 1 — haemoglobin >16.5 g/dL in men or >16.0 g/dL in women (haematocrit >49%/48%), or increased red cell mass; Major criterion 2 — bone marrow biopsy showing hypercellularity with trilineage proliferation; Major criterion 3 — JAK2 V617F or JAK2 exon 12 mutation. Diagnosis requires all 3 major criteria OR first 2 major + minor criterion (subnormal EPO). JAK2 positivity alone is not diagnostic as it also occurs in ET and PMF. Splenomegaly and low EPO are supportive but not sole major criteria.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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