Too many red blood cells (polycythemia)

What is it about ?

Polycythemia is an increase in the total volume of red blood cells in the blood. This volume is calculated by multiplying the number of red blood cells in the blood by their average volume (average blood volume, MCV).

As the total volume increases, the plasma (that is, the fluid in the blood without the blood cells) does not necessarily increase proportionately, and the blood therefore becomes more viscous. The most common cause of polycythemia is polycythemia vera, also called polycythemia vera, a chronic blood disease characterized by an excess of blood cells caused by an overproduction of the bone marrow where red blood cells, white blood cells and platelets are formed.

How to recognize it?

The increased viscosity of the blood increases the risk of clots forming in the arteries and veins, which can lead to a heart attack or stroke. The other signs can be are bleeding, fatigue, itching and nausea (see guide Vaquez’s disease).

How is the diagnosis made?

Polycythemia is often discovered by chance after a blood test, which shows an increase in the level of hemoglobin, hematocrit or the number of red blood cells. Hemoglobin is the protein that gives red blood cells their color and is responsible for transporting oxygen in the blood. The hematocrit is the volume occupied by red blood cells in the blood.

When diagnosing polycythemia, the doctor will try to determine its origin. For this, he will ask for additional tests: number of white blood cells, number of platelets, erythropoietin (EPO) level and oxygen level in the blood.

Relative polycythemia
Sometimes it can seem like there are more red blood cells in the blood. But in reality, it is the amount of plasma that has decreased. This is called relative polycythemia. This may be the case, for example, with dehydration, bleeding or heavy smoking.

Absolute polycythemia
In this case, the volume occupied by red blood cells is actually increased. This is called absolute polycythemia. A distinction is made between primary polycythemia and secondary polycythemia:

• Polycythemia primitive the most frequent is the polycythemia vera. It is a chronic disease of the bone marrow. Most often, the number of white blood cells and the number of platelets are also increased, unlike the level of EPO, which is decreased. The spleen is then often enlarged. You may also suffer from fatigue, itching, and nausea. A mutation in the JAK2 gene is present in the majority of cases.

• The secondary polycythemia is polycythemia caused by an increase in the level of EPO. EPO stimulates the production of red blood cells.
• The increase in EPO levels can be caused by a prolonged lack of oxygen in the tissues, for example in cases of prolonged stay at high altitude, certain chronic heart diseases, chronic lung disease, or in situations where the breathing is reduced (severe obesity, neurological disorders or heavy smoking). In these cases, the oxygen saturation measured in the blood is usually reduced (less than 92%). Oxygen saturation is the amount of oxygen bound to hemoglobin in red blood cells.
• The increase in the level of EPO may be linked to certain kidney diseases (cysts, tumors) or to certain cancerous diseases.

What can you do ?

If you have any doubts about this, consult your doctor. A blood test will quickly provide an explanation.

If your weight or your smoking is the cause of the problem, you are advised to lose weight,stop smoking and adopt a healthy lifestyle.

What can your doctor do?

For the treatment of polycythemia vera, consult the patient guide ‘Polycythemia vera or Polycythemia vera’.

In case of secondary polycythemia, the cause of polycythemia will be the subject of treatment. Bloodletting, done to reduce the risk of complications from hyperviscosity, for example in the central nervous system, is rarely necessary. In the case of relative polycythemia, the underlying cause will be treated, for example by correcting the dehydration, or by offering help with the problem of obesity or smoking.

Want to know more?

• Hematocrit – Lab Test Online

• Eating and gaining years of life is possible! (video) – CSS – Superior Health Council
• Stop smoking. It’s possible – Tabacstop

Are you looking for more specialized help?

• Smoking Assistance Center (CAF®) – FARES – Respiratory Affections Fund
• Tobacco specialists – FARES – Respiratory Affections Fund
• Find a registered dietitian – Professional Union of French-speaking dieticians
• Find a nutritionist doctor – Belgian Society of Nutritionist Doctors

Source

Foreign clinical practice guide ‘Polycythemia’ (2000), updated on 02.06.2017 and adapted to the Belgian context on 19.10.2019 – ebpracticenet