Erythrocytosis Vs Polycythemia: Know the Differences

Erythrocytosis Vs Polycythemia

Erythrocytosis Vs Polycythemia: While often used interchangeably, Erythrocytosis and Polycythemia have subtle differences. Both involve an increase in red blood cells, but Erythrocytosis focuses on the concentration of red blood cells in relation to blood volume, whereas Polycythemia refers to an absolute increase in both red blood cell count and hemoglobin, the protein carrying oxygen. Think of Erythrocytosis as "thicker blood" due to more cells packed in, while Polycythemia is "more blood" overall. This distinction matters because Polycythemia can have more serious implications due to the increased blood volume causing complications. So, Erythrocytosis can be a symptom of Polycythemia, but not all Erythrocytosis cases are Polycythemia. Remember, consulting a healthcare professional is crucial for proper diagnosis and treatment.

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Difference Between Erythrocytosis and Polycythemia

Erythrocytosis and Polycythemia are both conditions characterized by an increase in the number of red blood cells (erythrocytes) in the bloodstream. While they share similarities, they also have distinct differences. Highlighting the key difference between them:





Increase in red blood cell count

Increase in blood volume, red blood cells, or both

Primary vs. Secondary

Can be primary or secondary

Primarily refers to Polycythemia vera, may be secondary

Underlying Causes

Genetic mutations, increased EPO production

Abnormal proliferation of bone marrow stem cells


Generally milder, less specific

Headaches, dizziness, itching, fatigue

Risk of Complications

Less likely to lead to complications

Increased risk of thrombosis, stroke, and heart attack

Treatment Approach

Address underlying causes

Reduce blood viscosity, lower clotting risk


Depends on underlying cause and management

Influenced by complications and treatment response

Laboratory Findings

Elevated red blood cell count, normal hematocrit

Elevated red blood cell count, hematocrit, and hemoglobin

Associated Conditions

Seen in congenital heart defects, COPD

Often associated with Polycythemia vera, bone marrow disorders

Genetic Mutations

Associated with EPO receptor mutations

Linked to JAK2 gene mutations, other hematopoietic abnormalities

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What is Erythrocytosis?

Your blood becomes thicker than normal because of an excess of red blood cells, a condition known as erythrocytosis. This may occur as a result of underlying diseases like a bone marrow issue or transient causes like dehydration. The primary worry is an elevated risk of blood clots, although other symptoms such as headaches, dizziness, and skin redness can also occur.

Features of Erythrocytosis:

  • This is the defining feature of erythrocytosis, with a hematocrit (percentage of RBCs in blood) exceeding the normal range (41-53% for men, 38-48% for women).
  • The rare genetic disorder known as primary erythrocytosis causes the bone marrow to overproduce red blood cells. The more prevalent kind of secondary erythrocytosis is caused by underlying illnesses such as long-term lung disease, residing at high altitudes, or using certain drugs.
  • Certain people may not exhibit any symptoms at all from erythrocytosis, depending on the condition's severity and underlying aetiology. Others could experience weariness, headaches, dizziness, or vision issues.
  • The circumstance at hand and the underlying reason determine management. It might entail treating the underlying issue, using medications to lower RBC production, or phlebotomy (blood removal).

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What is Polycythemia?

A certain kind of erythrocytosis and polycythemia occurs when your bone marrow continuously overproduces red blood cells. The most common cause of this is a disorder known as polycythemia vera, which can also damage other types of blood cells. It needs continuous care and has an increased risk of consequences including leukaemia and blood clots.

Features of Polycythemia:

  • Polycythemia is a form of blood cancer where mutated bone marrow cells uncontrollably produce excessive RBCs, white blood cells, and platelets.
  • This medical condition causes elevated white blood cells and platelets in addition to increased red blood cells, which thickens the blood (viscosity).
  • Due to thicker blood flow, people with polycythemia frequently feel headaches, tiredness, dizziness, itching, and visual issues.
  • The goal of management is to stop the formation of new blood cells and avoid problems like blood clots. Usually, phlebotomy or medicine are used, perhaps in conjunction with low-dose radiation treatment.

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Similarities Between Erythrocytosis and Polycythemia

  • Erythrocytosis and Polycythemia, both conditions involve an increase in the number of red blood cells circulating in the bloodstream.
  • Both are considered hematological abnormalities due to the excessive production of red blood cells.
  • Both conditions can lead to complications, particularly related to increased blood viscosity and clotting.
  • Diagnosis for both conditions involves blood tests to measure red blood cell count, hematocrit, and hemoglobin levels.
  • Treatment for Erythrocytosis and Polycythemia, aims to reduce the risk of complications and normalize blood parameters to a certain extent.

While both terms describe an increase in red blood cells, Erythrocytosis and Polycythemia hold subtle distinctions. Erythrocytosis refers to a higher concentration of red blood cells relative to blood volume, regardless of the total red blood cell mass. This can occur due to dehydration or specific genetic mutations. Polycythemia, on the other hand, signifies an increased total red blood cell mass, leading to elevated levels of hemoglobin and hematocrit. It encompasses both primary (genetic) and secondary (underlying conditions like high altitude or smoking) causes. So, while all polycythemia is technically erythrocytosis, not all erythrocytosis qualifies as polycythemia. This distinction is crucial for diagnosis and treatment, as the underlying causes and potential complications differ between these conditions.

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What is the main difference between erythrocytosis and polycythemia?

Erythrocytosis refers specifically to an increase in red blood cell (RBC) count, whereas polycythemia encompasses an increase in RBC count along with other blood components such as white blood cells and platelets.

What are the similarities between erythrocytosis and polycythemia?

Both conditions involve an abnormal increase in the concentration of blood cells, which can lead to similar symptoms such as headaches, dizziness, and fatigue.

What are the symptoms of erythrocytosis and polycythemia?

Symptoms may include headaches, dizziness, blurred vision, itching (especially after a warm bath), fatigue, and in severe cases, increased risk of blood clots, stroke, or heart attack.

How are erythrocytosis and polycythemia diagnosed?

Diagnosis typically involves a complete blood count (CBC) to measure the levels of red blood cells, white blood cells, and platelets, along with additional tests such as genetic studies, bone marrow biopsy, and imaging scans.

Can erythrocytosis and polycythemia be treated?

Treatment depends on the underlying cause. Erythrocytosis may be managed by addressing the underlying condition, while treatment for polycythemia vera may include phlebotomy (removal of blood), medication to reduce blood cell production, or other therapies to manage symptoms and complications.