Polycythemia (Elevated Red Blood Cell Count)

  • Medical Author:
    Siamak N. 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.

  • Medical Editor: Charles Patrick Davis, MD, PhD
    Charles Patrick Davis, MD, PhD

    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.

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What are normal ranges of hematocrit, red cell counts, and hemoglobin?

  • Hematocrit is the ratio of the volume of red cells to the volume of whole blood. The normal range for hematocrit varies between sexes and is approximately 45% to 52% for men and 37% to 48% for women.
  • Red cell count signifies the number of red blood cells in a volume of blood. The normal range in men is approximately 4.7 to 6.1 million cells/ul (microliter). The normal range in women range from 4.2 to 5.4 million cells/ul, according to NIH (National Institutes of Health) data.
  • Hemoglobin is a protein in the red blood cells that carries oxygen and gives blood its red color. The normal range for hemoglobin may differ between the sexes and is approximately 13 to 18 grams per deciliter for men and 12 to 16 grams per deciliter for women.

What causes polycythemia?

Causes of polycythemia are primary or secondary. In primary polycythemia, abnormalities in red blood cell production cause an increase in red cell count. In secondary polycythemia, factors external to red blood cell production (for example, hypoxia, sleep apnea, certain tumors) result in polycythemia.

What are the causes of primary polycythemia?

Primary polycythemias are due to acquired or inherited genetic mutations causing abnormally high levels of red blood cell precursors. Primary familial and congenital polycythemia (PFCP) and polycythemia vera (PV) are in this category.

Polycythemia vera

Polycythemia vera is a rare condition. One study indicated that there were 65,243 patients with PV in the United States in 2003. Polycythemia vera is typically associated with an elevated white blood cell count (leukocytosis) and platelet count (thrombocytosis). An enlarged spleen (splenomegaly) and low erythropoietin levels are other clinical features of polycythemia vera.

Until recently, the exact mechanism of polycythemia vera was not well understood. In 2005, genetic mutations of the JAK2 gene were found to be responsible for most cases of polycythemia vera. These mutations are thought to possibly increase the sensitivity of the red blood cell precursors to erythropoietin, thereby, increasing red blood cell production.

Primary familial and congenital polycythemia (PFCP)

Primary familial and congenital polycythemia (PFCP) is also thought to be caused by genetic mutations resulting in increased responsiveness to normal levels of erythropoietin. Most cases are caused by different mutations to the EPOR gene.

Medically Reviewed by a Doctor on 2/23/2016

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