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Iron Deficiency in Polycythemia Vera: William Aird Reveals JAK2-Driven Erythropoiesis as The Key Cause
Aug 16, 2025, 14:00

Iron Deficiency in Polycythemia Vera: William Aird Reveals JAK2-Driven Erythropoiesis as The Key Cause

William Aird, Professor of Medicine at Harvard Medical School, shared an insightful thread on X:

”IRON DEFICIENCY (ID) IN POLYCYTEMIA VERA (PV)

  • Despite what we are taught, there is simply no evidence that iron deficiency, a common finding at presentation of PV, is caused by occult or overt bleeding.
  • Rather, ID is much more likely to be explained by high erythroid iron demand from JAK2-driven erythropoiesis, which rapidly consumes available iron stores and unmasks or worsens deficiency.
  • The iron cost of building a larger RBC mass (e.g., Hct 45→60 ≈ 740 mg) comes from stores. If stores are small, they can be drained in weeks, explaining iron deficiency at presentation without any bleeding.”

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