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Secondary Erythrocytosis

(Secondary Polycythemia)


Jane Liesveld

, MD, James P. Wilmot Cancer Institute, University of Rochester Medical Center

Reviewed/Revised Dec 2023

Erythrocytosis is increased production of red blood cells (erythrocytes).

Erythrocytosis may be

Secondary erythrocytosis develops generally as a result of a disorder that increases erythropoietin secretion. Erythropoietin is a hormone made in the kidneys that stimulates the bone marrow to produce red blood cells. As such, secondary erythrocytosis is not considered a myeloproliferative neoplasm. However, it is important for doctors to look for it because both primary and secondary erythrocytosis result in too many red blood cells.

Secondary erythrocytosis has many causes. It can be caused by oxygen deprivation, which can result, for example, from

Oxygen deprivation causes an increase in erythropoietin, which stimulates the bone marrow to produce more red blood cells so that the blood can carry more oxygen. People who spend long periods of time in environments or circumstances low in oxygen, such as people who live at high altitude, often develop erythrocytosis severe enough to cause symptoms (see ). In some birth defects of the heart Overview of Heart Defects About one in 100 babies is born with a heart defect. Some are severe, but many are not. Defects may involve abnormal formation of the heart's walls or valves or of the blood vessels that enter... read more , blood is misdirected away from the heart so that it cannot pick up oxygen, causing hypoxia (a low level of oxygen in the blood) and resulting in secondary erythrocytosis.

Other causes of secondary erythrocytosis include

  • Treatment with male hormones such as testosterone

  • Kidney problems, including tumors, cysts, and narrowing of the arteries that go to the kidneys

  • Tumors of the liver, brain, or adrenal gland

  • Genetic disorders that affect erythropoietin production (congenital erythrocytosis)

Male hormones such as testosterone stimulate production of erythropoietin.

Problems that decrease blood flow to the kidneys such as tumors, cysts, and narrowing of the arteries that go to the kidneys increase erythropoietin secretion.

Tumor-associated erythrocytosis can occur when certain tumors or cysts, such as of the kidneys, liver, brain, or uterus secrete erythropoietin.

Congenital erythrocytosis is present at birth and is usually caused by an inherited genetic disorder that affects the affinity of hemoglobin for oxygen or the response to hypoxia. (Hemoglobin is the molecule that carries oxygen within red blood cells. Hypoxia is when the level of oxygen in the blood is low.) These inherited genetic disorders are rare, but they are suspected when a person with erythrocytosis has family members who are also affected.

In relative erythrocytosis, there are not any extra red blood cells, but red blood cells seem to be at a high concentration because there is less fluid (plasma) in the bloodstream. The low plasma level can result from burns, vomiting, diarrhea, drinking an inadequate amount of fluids, or the use of medications that speed elimination of salt and water by the kidneys (diuretics).

Symptoms of Erythrocytosis

People with secondary erythrocytosis may have

  • Weakness

  • Tiredness

  • Headache

  • Light-headedness

  • Shortness of breath

Diagnosis of Erythrocytosis

  • Blood tests

  • Tests to determine the cause

Doctors ask about any drugs that may cause erythrocytosis. They measure the amount of oxygen and the level of erythropoietin in the blood. A high level of erythropoietin is often enough for doctors to diagnose secondary erythrocytosis. If the level is low, other tests for the primary erythrocytosis (polycythemia vera Polycythemia Vera Polycythemia vera is a myeloproliferative neoplasm of the blood-producing cells of the bone marrow that results in overproduction of all types of blood cells. Polycythemia vera is due to mutations... read more ) will be done.

Sometimes other specialized tests are done, especially when doctors need to determine an uncommon cause of erythrocytosis. These may include tests to look for a hormone disorder or a hidden tumor that might be causing other symptoms.

Congenital erythrocytosis is usually diagnosed when a person develops symptoms at an early age or has family members who also have erythrocytosis. In addition to blood tests, doctors may do genetic testing to determine the specific cause.

Treatment of Erythrocytosis

  • Treatment of cause

  • Phlebotomy

Secondary erythrocytosis that is caused by oxygen deprivation may be treated with oxygen. People who smoke are advised to quit and are offered treatments to assist quitting Smoking Cessation Most people who smoke want to quit and have tried doing so with limited success. Effective tools to help quit smoking include counseling, nicotine replacement products, and medications. While... read more . Any underlying disorder that is causing the oxygen deprivation and secondary erythrocytosis is treated as effectively as possible. In some people, phlebotomy (in which some of the person's blood is removed) is used to lower the number of red blood cells. It is rare that phlebotomy is needed in secondary erythrocytosis.

In tumor-associated erythrocytosis, removal of the tumor can be curative. Treating a specific hormone disorder or discontinuing a medication that can cause secondary erythrocytosis may also be curative.

Relative erythrocytosis is treated by giving fluids by mouth or intravenously and by treating any underlying conditions that are contributing to the low plasma level.

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