Erythrocytosis (Polycythemia)

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A comprehensive overview for clinicians, students, and curious patients

Introduction to Polycythemia

Polycythemia is a condition characterized by an abnormally high number of red blood cells in the bloodstream. This increase in red cell mass thickens the blood, making it flow more slowly and increasing the risk of serious complications such as blood clots, strokes, or heart attacks. Polycythemia can arise from a variety of underlying causes, ranging from rare bone marrow disorders to chronic health conditions that reduce oxygen levels in the body. In some cases, it may be triggered by external factors such as medications or environmental exposures. Effective diagnosis and treatment—often involving blood removal (phlebotomy) and medications—are essential to reduce symptoms and prevent potentially life-threatening outcomes. Understanding the different types and causes of polycythemia is critical for proper management and care.

1. Definition and Basic Concepts

Term

Core idea

Key laboratory hallmark

Typical drivers

Absolute erythrocytosis

True expansion of total red‑cell mass (RCM)

↑ RBC mass on isotope study or markedly elevated hematocrit/hemoglobin

Primary bone‑marrow disorders or sustained erythropoietin (EPO) stimulation

Relative (spurious) erythrocytosis

Normal RCM but ↓ plasma volume (hemoconcentration)

High hematocrit but normal red‑cell mass

Dehydration, diuretics, stress‑polycythemia (“Gaisböck syndrome”)




A hematocrit (Hct) > 52 % in men or > 48 % in women (or hemoglobin > 18.5 g/dL and > 16.5 g/dL, respectively) should prompt a structured evaluation.





2. Classification

  1. Primary (EPO‑independent) erythrocytosis

    • Polycythemia vera (PV): Chronic myeloproliferative neoplasm driven by JAK2 mutations (≈ 95 % V617F, ≈ 3 % exon 12).

    • Primary familial/congenital polycythemias (rare): Germ‑line defects in EPO receptor, VHL, EPAS1 (HIF‑2α).

  2. Secondary (EPO‑driven) erythrocytosis

    • Hypoxia‑mediated – COPD, obstructive sleep apnea (OSA), cyanotic heart disease, chronic high‑altitude exposure, heavy smoking (carbon‑monoxide binding).

    • Pathologic EPO secretion – Renal cell carcinoma, hepatocellular carcinoma, uterine fibroids, cerebellar hemangioblastoma, pheochromocytoma, adrenal adenoma.

    • Drug‑ or hormone‑related – Exogenous EPO, testosterone or anabolic‑androgenic steroids, SGLT2 inhibitors (mild).

  3. Relative (spurious) erythrocytosis – Plasma‑volume contraction (burns, dehydration, diuretics, severe vomiting).

3. Pathophysiology Snapshot

  • Elevated red‑cell mass → ↑ whole‑blood viscosity

  • Hyperviscosity slows microvascular flow → tissue hypoxia and thrombogenesis

  • In PV, excessive platelets and leukocytes add a prothrombotic milieu and chronic inflammatory signaling (JAK‑STAT activation).

4. Clinical Presentation

“Hyper‑viscosity” symptoms

Thrombotic/vascular events

PV‑specific clues

Headache, dizziness, tinnitus

Deep‑vein thrombosis, stroke, MI, Budd–Chiari syndrome, portal‑splenic thrombosis

Aquagenic pruritus (itch after warm shower), erythromelalgia (burning hands/feet), facial plethora, splenomegaly

Visual blurring, choreiform movements

Microvascular angina, claudication

Gout, peptic ulcers (histamine release), leukocytosis






5. Step‑wise Diagnostic Approach


  1. Confirm erythrocytosis

    • CBC repeat × 2, consider plasma‑volume/RBC‑mass study if results are borderline or suspicion of relative polycythemia.

  2. Rule out primary PV

    • JAK2 V617F (first‑line), if negative test exon 12.

    • Bone‑marrow biopsy if mutation‑negative but strong clinical suspicion.

  3. Assess for secondary drivers

    • Serum EPO: Low/normal → suggests PV; High → secondary.

    • Arterial oxygen saturation, carboxyhemoglobin (smokers), overnight oximetry or polysomnography, chest X‑ray/CT, abdominal ultrasound/CT (renal masses), serum testosterone level.

  4. Additional labs: Ferritin (PV is often iron‑deficient), LDH, uric acid, basic metabolic panel, coagulation profile.


6. Management Principles

Scenario

First‑line measures

Additional / special situations

Polycythemia vera

Therapeutic phlebotomy to keep Hct < 45 % (men) or < 42 % (women); low‑dose aspirin 81 mg daily (unless contraindicated)

Cytoreduction when high‑risk (age ≥ 60 y or prior thrombosis): hydroxyurea; alternatives—interferon‑α (preferred in pregnancy or younger pts), busulfan (elderly), ruxolitinib (JAK inhibitor) for HU‑intolerant/resistant

Secondary erythrocytosis

Treat underlying cause: optimize COPD/OSA therapy (CPAP), resect EPO‑secreting tumor, adjust exogenous testosterone/EPO

Phlebotomy only if symptomatic hyperviscosity or Hct > 56 % despite correction of driver; avoid iron deficiency

Relative erythrocytosis

Re‑hydrate, stop offending diuretics, manage stress

 





Lifestyle counseling
Strict smoking cessation, maintain hydration, regular exercise within guidelines, control cardiovascular risk factors (BP, lipids, glucose), avoid iron supplementation unless deficient.


7. Complications & Prognosis

  • Thrombosis – leading morbidity/mortality cause in PV (arterial > venous).

  • Hemorrhage – paradoxical bleeding in 5–10 % of PV (acquired von Willebrand disease when Hct very high).

  • Myelofibrotic or leukemic transformation – PV → post‑PV myelofibrosis (≈ 10‑15 % at 15 y) or AML (≈ 3–10 % lifetime).

  • Quality‑of‑life issues – chronic pruritus, fatigue, concentration difficulties.

Hemorrhage in polycythemia vera?

Can polycythemia vera cause acquired von Willebrand disease?

AVWS associated with myeloproliferative neoplasia (MPN) primarily results from adsorption of VWF to transformed blood cells, in particular platelets. It has been reported in essential thrombocythemia and polycythemia vera, but also in chronic myeloid leukemia, primary myelofibrosis, and sometimes in acute leukemia.
What is the function of ADAMTS13? 
The enzyme ADAMTS13 breaks down von Willebrand factor into smaller pieces to regulate its interaction with platelets.

With modern risk‑adapted therapy, median survival in PV now exceeds 18–20 years; patients achieving strict Hct control have stroke/MI rates comparable to the general population.

8. Follow‑up & Monitoring

Parameter

Interval

Notes

CBC, differential

Every 3 mo while titrating; q6–12 mo when stable

Watch for iron deficiency (falling MCV) or leukocytosis

Ferritin, iron studies

At diagnosis, then if MCV ↓ or fatigue ↑

Iron store repletion in PV is individualized

Symptom assessment (pruritus, microvascular)

Every visit

MPN‑SAF TSS questionnaire can help quantify burden

JAK2 allele burden (PV)

Baseline, then if considering cytoreduction change

Rising burden may herald disease progression

Bone‑marrow biopsy

At diagnosis (optional); if cytopenias, splenomegaly, or ↑ LDH

Evaluate for post‑PV myelofibrosis


9. Special Situations

Pregnancy – Aim Hct < 45 % via phlebotomy; low‑dose aspirin; consider interferon‑α if cytoreduction needed.



High‑altitude residents – “Chronic mountain sickness” can mimic PV; treatment centers on acclimatization breaks, supplemental oxygen over 3,000 m.




Athletes – Distinguish physiologic “sports polycythemia” (↑ plasma volume + modest RBC mass) from doping with EPO/testosterone; look for suppressed EPO level in the former.




10. Key Take‑Home Messages

  1. Always verify true red‑cell mass; do not mistake dehydration for PV.

  2. Low EPO + JAK2 mutation = PV until proven otherwise.

  3. Target hematocrit ≤ 45 % saves lives—confirmed by CYTO‑PV RCT.

  4. Treat the root cause in secondary erythrocytosis; phlebotomy is supportive, not curative.

  5. Regular follow‑up is crucial to prevent thrombosis and detect progression early.

Disclaimer: This educational article is not a substitute for individualized medical care. Patients should discuss diagnosis and treatment options with their qualified healthcare professional.

References:

Polycythemia: https://www.ncbi.nlm.nih.gov/books/NBK526081/

Polycythemia: https://www.testmottagningen.se/en/symtom/hjart-och-karlsjukdomar/polycytemi/#:~:text=Polycythemia%20%2D%20too%20many%20red%20blood%20cells,cells%20%2D%20an%20increased%20amount%20of%20erythrocytes.

Red Blood Cell Disorders: https://health.ucdavis.edu/conditions/blood-disorders/red-blood-cell-disorders

Red Blood Cell (RBC) Count: https://www.healthline.com/health/rbc-count

Polycythemia Everything you need to know: https://www.medicalnewstoday.com/articles/polycythemia


© 2000-2030 Sieglinde W. Alexander. All writings by Sieglinde W. Alexander have a fife year copy right. Library of Congress Card Number: LCN 00-192742

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