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Hereditary Erythrocytosis vs Polycythemia Vera: Key Differences

Feb 9, 2026

Key takeaways

  • Hereditary erythrocytosis is a germline condition caused by inherited or de novo variants that increase red blood cell production, usually without affecting other blood cell types.
  • Polycythemia vera (PV) is an acquired myeloproliferative neoplasm driven by somatic JAK2 mutations and often involves elevations in multiple blood cell lines.
  • Distinguishing between the two relies on genetic testing, erythropoietin (EPO) levels, and blood count patterns, not hemoglobin alone.


Overview

Both hereditary erythrocytosis and polycythemia vera present with elevated hemoglobin and hematocrit, but they arise from fundamentally different mechanisms. Hereditary erythrocytosis reflects lifelong dysregulation of oxygen sensing or erythropoietin signaling, whereas PV is a clonal stem cell disorder with malignant potential. Clear differentiation is essential to avoid misdiagnosis. [1][2][3]

Cause and genetics

Hereditary erythrocytosis results from germline genetic variants, which may be inherited or occur de novo (reported in more than 10% of cases). These variants fall into two broad categories: [1][2]


  • Primary hereditary erythrocytosis: variants in EPOR, leading to hypersensitivity to erythropoietin and increased red cell production despite low EPO levels. [1]
  • Secondary hereditary erythrocytosis: variants in oxygen-sensing pathway genes (VHL, EGLN1/PHD2, EPAS1/HIF-2α), resulting in inappropriately normal or elevated erythropoietin production. [1][2]


Polycythemia vera is caused by acquired somatic mutations in JAK2 (V617F or exon 12) in approximately 98% of patients, leading to cytokine-independent proliferation of blood cells. [3]

Blood count patterns and laboratory clues

Hereditary erythrocytosis typically presents with isolated erythrocytosis, while platelet and white blood cell counts remain normal. Erythropoietin levels vary by genotype, often low in EPOR-related disease and normal or elevated in oxygen-sensing variants. [1][2]

In contrast, PV frequently shows panmyelosis, with elevations in red cells, platelets, and/or leukocytes. Serum erythropoietin is usually suppressed and serves as a supportive diagnostic clue in the diagnostic workup. [3]

Clinical implications and management

PV carries a higher thrombotic risk and a small but real risk of progression to myelofibrosis or acute leukemia. Management prioritizes maintaining a hematocrit below 45%, typically using phlebotomy, low-dose aspirin, and cytoreductive therapy in higher-risk patients. [3]

Hereditary erythrocytosis does not progress to myeloid malignancy. Treatment is individualized and often conservative, focusing on symptom relief, avoidance of hypoxia, and selective use of phlebotomy or aspirin when clinically indicated. [1][2]

Final thoughts

Although hereditary erythrocytosis and polycythemia vera can look similar on routine blood tests, they differ in origin, risk profile, and treatment goals. Germline versus somatic genetics is the central distinction, making targeted testing essential for accurate diagnosis and appropriate care. [1][2][3]

References

  1. Gangat, N., Szuber, N., & Tefferi, A. (2023). JAK2-unmutated erythrocytosis: 2023 update on diagnosis and management. American Journal of Hematology, 98(6), 889–899.
  2. McMullin, M. F. (2021). Genetic background of congenital erythrocytosis. Genes, 12(8), 1151.
  3. Tefferi, A., & Barbui, T. (2023). Polycythemia vera: 2024 update on diagnosis, risk-stratification, and management. American Journal of Hematology, 98(9), 1465–1487.