What causes secondary polycythemia?

Updated: Jul 20, 2020
  • Author: Srikanth Nagalla, MBBS, MS, FACP; Chief Editor: Sara J Grethlein, MD, FACP  more...
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Answer

Secondary polycythemia is defined as an absolute increase in red blood cell mass that is caused by enhanced stimulation of red blood cell production. In contrast, polycythemia vera is characterized by bone marrow with an inherent increased proliferative activity. [1, 2, 6, 7, 8, 9]  Approximately two thirds of patients with polycythemia vera have elevated white blood cell (granulocyte, not lymphocyte) counts and platelet counts. [10] No other causes of polycythemia/erythrocytosis are associated with elevated granulocyte or platelet counts.

Enhanced erythroid stimulation can be a physiologic response to generalized or localized tissue hypoxia, [11] as in the following settings:

  • Decreased ambient oxygen concentration, as occurs in people living at high altitudes, can result in compensatory erythrocytosis as a physiologic response to tissue hypoxia. [12]

  • Chronic obstructive pulmonary disease is commonly due to a large amount of ventilation in poor gas exchange units (high ventilation-to-perfusion ratios). [13]

  • Alveolar hypoventilation can result from periodic breathing and oxygen desaturation (sleep apnea) or morbid obesity (Pickwickian syndrome).

  • Cardiovascular diseases associated with a right-to-left shunt (arteriovenous malformations) can result in venous blood mixing in the arterial system and delivering low oxygen levels to tissues.

  • Hemoglobin abnormalities associated with high oxygen affinity and congenital defects can lead to oxidized or methemoglobin. These conditions are usually familial.

  • Exposure to carbon monoxide by smoking or working in automobile tunnels results in an acquired condition. [14, 15] Carboxyhemoglobin has a strong affinity for oxygen.


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