Polycythemia, or erythrocytosis, refers to an increase in circulating red blood cell mass, which can present as an elevated red blood cell count, hemoglobin, or hematocrit. The term erythrocytosis more accurately refers to any increase in red blood cells, whereas polycythemia refers to an increase in the production of other blood cells (such as white blood cells and platelets) in addition to red blood cells, as seen in polycythemia vera.

An increased concentration of red blood cells (RBCs) makes the blood thicker, leading to problems with circulation and issues like headaches, dizziness, and even heart attack.

The goal of treatment for polycythemia is not only to reduce the concentration of RBCs in the blood, but to alleviate symptoms and prevent complications like stroke and pulmonary embolism.

Common symptoms

Polycythemia does not usually cause symptoms unless the red blood cell count is very high, and may only be apparent on a blood test. In other cases, however, polycythemia may cause symptoms such as:

Persistent headache;
Blurry vision;
Extreme fatigue;
Itchy skin;
Dizziness.

It is important to have regular blood tests and to contact your doctor immediately if you experience any symptoms related to polycythemia. This is because thickening of the blood related to an increase in RBCs increases the risk for stroke, heart attack, and pulmonary embolism.

Making the diagnosis

The diagnosis of polycythemia is made based on the results of a complete blood count (CBC), in which the hemoglobin (Hgb) and hematocrit (Hct) are elevated in addition to the RBCs.

Polycythemia can be suspected and further investigated when the RBCs are greater than 5.4 mcL in women and 5.9 mcL in men. Reference ranges may differ slightly depending on the lab where the blood is drawn.

Common causes

The main causes of polycythemia include:

Genetic mutations;
Dehydration;
Cardiovascular disease;
Respiratory conditions;
Obesity;
Tobacco use;
Cushing's disease;
Liver problems;
Chronic myeloid leukemia (CML);
Lymphoma;
Kidney (renal) issues;
Tuberculosis.

Red blood cell count can also increase from prolonged use of corticosteroids, vitamin B12 supplements, and medications used to treat breast cancer.

Types of polycythemia

Polycythemia can be classified into different types based on the results of the CBC and the cause of the elevation in RBCs:

Primary erythrocytosis, also called polycythemia vera, is a type of rare blood cancer characterized by the abnormal production of blood cells related to a genetic condition.
Relative erythrocytosis, which is characterized by a decrease in plasma volume (from dehydration, for example) that is not necessarily indicative of a major problem with the production of red blood cells;
Secondary erythrocytosis, which results from conditions that may increase not only the number of red blood cells but other lab values as well.

It is important to identify the cause of polycythemia as this will guide the best treatment and avoid the development of other symptoms and complications.

Treatment options

Treatment of polycythemia involves a hematologist, a doctor that specializes in blood disorders. Treatment will depend on the cause of the elevated RBCs.

The goal of treatment is typically to reduce the number of red blood cells, improving blood flow. This can relieve symptoms and reduce the risk of complications. In the case of polycythemia vera, therapeutic phlebotomy (blood draws) may be recommended, in which excess red blood cells are removed.

A doctor may also utilize medications, such as aspirin, to thin the blood and reduce the risk of blood clots. Other medications, such as hydroxyurea or Interferon alpha, may also be used to reduce the quantity of red blood cells.