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- Polycythemia facts
- 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 are the risk factors for polycythemia?
- What is stress 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?
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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.
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.