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Apparent Polycythaemia — RACP Adult Medicine MCQ

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HardHaematologyApparent PolycythaemiaRACP Adult Medicine

A heavy smoker with obesity has haemoglobin 178 g/L, normal measured red-cell mass, reduced plasma volume, normal oxygen saturation and negative JAK2 testing. What is the best classification?

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Correct answer: A — Relative erythrocytosis caused by plasma-volume contraction

The best answer is “Relative erythrocytosis caused by plasma-volume contraction”. An elevated haemoglobin with normal red-cell mass and reduced plasma volume is relative erythrocytosis, historically described with smoking, hypertension, alcohol or obesity. Absolute primary and secondary erythrocytosis increase red-cell mass. Management targets volume status and cardiovascular and smoking risks rather than phlebotomy by default.

Reference: Leukaemia Foundation: Myeloproliferative neoplasms: https://www.leukaemia.org.au/types-of-blood-cancer/myeloproliferative-neoplasms-mpn/