Can a patient have polycythemia vera despite a mean corpuscular volume of 87.6 fL?

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Last updated: September 8, 2026 • View editorial policy

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Yes, you can absolutely have polycythemia vera with an MCV of 87.6 fL

An MCV of 87.6 fL does not exclude polycythemia vera (PV) and is actually quite compatible with the diagnosis, particularly in the setting of iron deficiency or early disease. In fact, iron deficiency is common in PV patients and can mask the typical erythrocytosis while lowering the MCV, creating what is sometimes called "masked PV" 1, 2.

Why MCV is Not a Diagnostic Criterion

The WHO diagnostic criteria for PV focus on:

  • Major criteria: Elevated hemoglobin (≥18.5 g/dL in men, ≥16.5 g/dL in women) or increased red cell mass, plus JAK2 mutation (V617F or exon 12)
  • Minor criteria: Bone marrow hypercellularity with panmyelosis, low serum erythropoietin, and endogenous erythroid colonies 1

MCV is notably absent from these criteria because it varies significantly in PV patients depending on iron status.

The Iron Deficiency Connection

How Iron Deficiency Modifies PV Presentation

  • Iron deficiency is extremely common in PV due to chronic phlebotomy therapy and increased iron utilization by the expanded red cell mass 3
  • When iron deficiency develops, the MCV typically decreases below normal (microcytosis), often into the 70-85 fL range
  • Your MCV of 87.6 fL is actually in the low-normal range, which is consistent with either early iron restriction or borderline iron deficiency 3
  • Studies show that active pruritus in PV correlates significantly with low MCV, suggesting iron deficiency plays a pathogenic role 3

Clinical Implications

The guidelines explicitly acknowledge this issue: "In routine clinical practice, one should not be prevented from making a working diagnosis of PV, in the presence of iron deficiency, just because the WHO criteria are not met" 1. This means:

  • Iron deficiency can lower hemoglobin/hematocrit below diagnostic thresholds while the patient still has true PV
  • The diagnosis should be based on the constellation of findings including JAK2 mutation status, erythropoietin levels, and bone marrow findings
  • Some patients present with "masked PV" where iron restriction attenuates or completely obscures typical erythrocytosis 2, 4

Diagnostic Approach When MCV is Normal-Low

When evaluating for PV with a borderline or low-normal MCV:

  1. Check JAK2 V617F mutation (present in ~95% of PV cases) 1

  2. Measure serum erythropoietin (should be low or inappropriately normal in PV) 1

  3. Assess iron studies (ferritin, transferrin saturation, serum iron) to identify iron deficiency 2

  4. Look for other features:

    • Leukocytosis or thrombocytosis
    • Splenomegaly
    • History of thrombosis (especially unusual sites like splanchnic veins) 2, 4
    • Pruritus (particularly aquagenic) 3

  5. Consider bone marrow biopsy if JAK2 is positive but hemoglobin/hematocrit are normal or only mildly elevated 1

Special Scenarios

Masked PV with Normal Blood Counts

Recent case reports document JAK2-positive PV presenting with completely normal hemoglobin and hematocrit 4. These patients may present with:

  • Thrombosis as the first manifestation (particularly portal/splanchnic vein thrombosis) 2, 4
  • Normal or near-normal MCV (83-87 fL range documented) 2
  • Evidence of iron restriction on biochemical testing 2

Plasma Volume Expansion

In PV, plasma volume typically increases along with red cell mass 5. This can dilute the hematocrit measurement, making it appear falsely normal even when true red cell mass is elevated. The MCV remains unaffected by plasma volume changes.

Common Pitfalls to Avoid

  • Don't dismiss PV based solely on normal or low-normal MCV - this is not part of diagnostic criteria
  • Don't wait for "classic" erythrocytosis if other features suggest PV (JAK2 mutation, low EPO, thrombosis)
  • Don't assume microcytosis means only iron deficiency - it's often a feature of treated or undertreated PV
  • Don't forget that iron deficiency can coexist with and mask PV - the guidelines explicitly allow diagnosis in this setting 1

Bottom Line

An MCV of 87.6 fL is entirely compatible with PV and should not deter you from pursuing the diagnosis if other clinical or laboratory features are suggestive. The key is to test for JAK2 mutations, measure erythropoietin, assess iron status, and look for associated features like leukocytosis, thrombocytosis, splenomegaly, or unexplained thrombosis 1, 2.

References

5
Research

Polycythemia Vera.

Current treatment options in oncology, 2018

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This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.