Polycythemia vera (PV) is distinguished from secondary polycythemia by the presence of which molecular mutation in >95% of cases?

• A BCR-ABL1 fusion gene
• B CALR exon 9 insertion/deletion
• C MPL W515K/L mutation
• D JAK2 V617F point mutation ✓

Explanation

The JAK2 V617F point mutation is present in >95% of polycythemia vera cases and ~50–60% of essential thrombocythemia and primary myelofibrosis. It is the pathognomonic mutation for PV diagnosis per WHO 2022 criteria. CALR mutations are found in ~25–35% of ET and PMF cases without JAK2 V617F. MPL mutations occur in ~3–5% of ET/PMF. BCR-ABL1 defines chronic myeloid leukemia (CML). The distinction from secondary polycythemia (low EPO in PV vs. elevated EPO in secondary) is supported by JAK2 testing.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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Written and medically reviewed by the StethoPrep medical team.