Polycythemia (High Red Blood Cell Count) (cont.)
Siamak T. Nabili, MD, MPH
Dr. Nabili received his undergraduate degree from the University of California, San Diego (UCSD), majoring in chemistry and biochemistry. He then completed his graduate degree at the University of California, Los Angeles (UCLA). His graduate training included a specialized fellowship in public health where his research focused on environmental health and health-care delivery and management.
Charles Patrick Davis, MD, PhD
Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.
In this Article
- What is polycythemia?
- What are normal ranges of hematocrit, red cell counts, and hemoglobin?
- What causes polycythemia?
- What are the causes of primary polycythemia?
- What are the common causes of secondary polycythemia?
- Can other sources of erythropoietin (EPO) cause polycythemia?
- What is relative polycythemia?
- What is stress polycythemia?
- What are the risk factors for polycythemia?
- What are the symptoms of polycythemia?
- When should I see a doctor about polycythemia?
- How is polycythemia diagnosed?
- What is the treatment for polycythemia?
- What are the complications of polycythemia?
- Can polycythemia be prevented?
- What is the outlook (prognosis) for polycythemia?
- Polycythemia At A Glance
- Find a local Hematologist in your town
What are the common causes of secondary polycythemia?
Secondary polycythemia is usually due to increased erythropoietin (EPO) production either in response to chronic hypoxia (low blood oxygen level) or from an erythropoietin secreting tumor.
Chronic hypoxia
Common conditions causing chronic hypoxia are chronic lung diseases such as:
- emphysema and
chronic bronchitis which are collectively known as
chronic obstructive pulmonary
disease (COPD) or hypoventilation syndrome,
- chronic heart diseases (congestive heart
failure, or abnormal flow of blood from the right side to the left side of the
heart),
- sleep apnea, and
- pulmonary hypertension.
Abnormal blood flow to the kidneys can be perceived by the kidneys as decreased oxygenation (renal hypoxia), even though, other tissues may have normal oxygenation. Renal hypoxia may promote an increase in erythropoietin production. This condition can occur after kidney transplantation or narrowing of renal arteries (blood vessels supplying the kidneys).
People living in high altitudes can develop polycythemia. In high altitudes, increased red blood cell production occurs in order to compensate for the low ambient oxygen levels and inadequate tissue oxygenation.
Rare congenital defects in the hemoglobin molecule, such as 2, 3-BPG deficiency, can result in a higher oxygen affinity by hemoglobin. In these conditions, oxygen is held on tightly by hemoglobin and is less readily released from hemoglobin to the tissues. The resulting tissue hypoxia from poor oxygen delivery may lead to polycythemia.
Erythropoietin secreting tumors
Certain tumors can release increased amount of erythropoietin. The most common erythropoietin secreting tumors are:
- liver cancer
(hepatocellular carcinoma),
- kidney cancer (renal cell carcinoma),
- adrenal adenoma (adenocarcinomas), and
- uterine (womb) tumors.
Occasionally, benign kidney cysts and kidney obstruction (hydronephrosis) can also secrete extra erythropoietin causing polycythemia.
A rare genetic condition, called Chuvash polycythemia, causes increased activity of the gene that produces erythropoietin. The overproduction of erythropoietin causes polycythemia.
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