Published May 12, 2023 by

Polycythemia: Definition, Causes, Diagnosis and Treatment


General Discussion 

Polycythemia, also called polyglobulia or erythrocytosis, is a disease characterized by an excess of red blood cells produced by the bone marrow. This overproduction makes the blood thicker and less able to circulate in the bloodstream and organs, causing symptoms such as headache, dizziness, excessive tiredness, clouded vision, or a burning sensation in the body's extremities. 

The causes of polyglobulia are unknown, and symptoms usually appear between the ages of 50 and 60, and can lead to serious complications, such as blood clots or swelling of the spleen. 

The treatment of polyglobulia should be indicated by the general practitioner or hematologist who may indicate phlebotomy, which is the removal of blood similar to that performed in blood donations, reducing the number of red blood cells in the blood, or using medicines to relieve symptoms and prevent complications, such as a heart attack or stroke, for example.

Types of Polycythemia 

Polycythemia can be classified into some types according to the blood count result and the cause of the increased number of red blood cells: 

Primary polycythemia: also called polycythemia vera, which is a genetic disorder characterized by abnormal production of blood cells. Understand more about polycythemia vera; 

Relative polycythemia: which is characterized by an increase in the number of red blood cells due to a decrease in plasma volume, as in the case of dehydration, for example, not necessarily indicating that there was a greater production of red blood cells; 

Secondary polycythemia: which occurs due to diseases that can lead to an increase not only in the number of red blood cells, but also in other laboratory parameters. 

It is important to identify the cause of polycythemia so that the best type of treatment can be established, avoiding the appearance of other symptoms or complications.

Possible Causes 

The causes of polyglobulia can be divided into different types depending on what led to the development of excessive production of red blood cells and include: 

1. Apparent polycythemia  

Apparent polycythemia is characterized by the normal count of red blood cells in the blood, but there is a lower production of blood plasma, which is the liquid part of the blood. In this way, with less plasma, the blood becomes thicker. 

Generally, this type of polyglobulia is caused by being overweight, smoking cigarettes, excessive alcohol consumption or the use of certain medications such as diuretics, for example. 

2. Relative polycythemia 

Relative polyglobulia, also called pseudopolyglobulia, is similar to apparent polycythemia, in which red blood cell production is normal but blood plasma volume is reduced, increasing blood viscosity. 

This type of polyglobulia is mainly caused by dehydration, which is a condition characterized by the body eliminating more water than the amount that is ingested. 

3. Absolute polycythemia

Absolute polycythemia, also called real polyglobulia, occurs when the body produces too many red blood cells, and can be classified according to the origin of the problem into two types: 

Primary polyglobulia: is caused by a deficiency in the cells produced by the bone marrow that transform into red blood cells. The most common type of this type of polyglobulia is polycythemia vera. Understand better what polycythemia vera is and its causes; 

Secondary polyglobulia: is caused by excessive production of red blood cells due to other conditions such as being at a high altitude, obstructive sleep apnea, heart or lung disease that leads to reduced levels of oxygen in the body, or a tumor in the kidneys, for example.

It is important to identify the cause of polycythemia so that the best type of treatment can be established, preventing the appearance of other symptoms or complications. 

Symptoms of Polycythemia  

People suffering from polycythemia vera usually have no symptoms for years. Initial symptoms are usually, 




Dizziness or feeling faint 

Shortness of breathe 

Night sweats 

Itching after a shower or bath 

Vision may be distorted, and people may experience blind spots or see flickering of light (ocular migraine). 

-People may experience bleeding from the digestive tract or gums and more bleeding than expected from minor cuts. 

-The skin, especially on the face, may become reddened. People may experience itching all over the body, especially after bathing. People may experience redness and a burning sensation in the hands and feet (erythromelalgia). More rarely, they may experience bone pain.

-Sometimes a blood clot causes the first symptoms. The increase in red blood cells in polycythemia vera makes the blood thicker and more likely to clot more than normal. A clot can form in virtually any blood vessel, including those in the arms, legs (which causes deep vein thrombosis), heart (which causes a heart attack), brain (which causes stroke), or the lungs (which causes pulmonary embolism). Blood clots can also block blood vessels that drain blood from the liver (Budd-Chiari syndrome), particularly in young women. 

-In some people, the number of platelets (cell-like particles in the blood that help the body form clots) increases (thrombocythemia). Although it may be assumed that an increased number of platelets will always cause excessive blood clotting, a very high number of platelets in people with polycythemia vera can actually cause bleeding by affecting other parts of the body's clotting system.

-In some people, iron deficiency may develop. 

-The liver and spleen may enlarge as both organs begin to produce blood cells (see also enlarged spleen). As the liver and spleen increase in size, a feeling of abdominal fullness may develop. 

-Excess red blood cells can be associated with gastric ulcers, gout, and kidney stones. In rare cases, polycythemia vera turns into leukemia.


Polycythemia vera is suspected in patients with characteristic physical findings and/or elevated hemoglobin and hematocrit levels on blood count. 

Rule out secondary causes of polycythemia (elevated EPO levels): 

*high altitude 

*chronic hypoxia 

*Paraneoplastic syndrome (renal cell carcinoma) 

Other laboratory findings of primary PV: 

1.Blood count and biochemistry: 


-Hemoglobin and hematocrit 



-Uric acid and B12 (not required for diagnosis) 






2.Peripheral smear: 

Findings depend on the stage at the time of diagnosis. 

-Erythrocytosis (excess red blood cells) 

-Dacryocytes (teardrop shaped red blood cells) 

-Poikilocytosis (abnormally shaped red blood cells) 

-Circulating nucleated red blood cells 

-Hypochromia and microcytosis in case of iron deficiency 


-Leukocytosis in the absence of fever or infection

3.Test for JAK2, CALR, and LNK mutations (done sequentially) 

4.Bone marrow biopsy: 

-No bone marrow findings absolutely differentiate PV from other disorders with erythrocytosis. 

-Increased cellularity (versus fibrosis) 

-Usually shows panmyelosis 

-Large, clustered megakaryocytes 

-Occasional increase in reticulin fibers

Treatment Procedure 

The treatment of polyglobulia is aimed at relieving symptoms, preventing complications such as blood clots, as well as treating its cause, and includes: 

1.Therapeutic phlebotomy or bloodletting: 

It is the simplest and fastest way to reduce the number of red blood cells in the blood, as blood is removed and is recommended in cases of primary polyglobulia, history of blood clot formation or the appearance of symptoms of polyglobulia . 

2.Use of drugs to reduce the amount of red blood cells, such as hydroxyurea or interferon: 

these drugs should always be used with medical advice and should not be used by pregnant women or those planning a pregnancy;

3.Use of anticoagulants, such as acetylsalicylic acid: 

may be indicated by the doctor to make the blood more fluid and reduce the risk of clot formation; 

It is important to treat the disease that may have caused the polyglobulia. Also, apparent polycythemia may improve by stopping smoking or reducing alcohol intake, for example.

Possible complications

Complications that polycythemia can cause include: 

-Enlargement of the spleen; 

-Formation of blood clots; 


-Stroke or stroke; 

-heart attack; 

-Pulmonary embolism; 

-Deep vein thrombosis; 


-Peptic ulcer. 

Although rare, polycythemia can also give rise to other complications such as myelofibrosis, myelodysplastic syndrome or acute leukemia, for example.