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Polycythemia
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Polycythemia, also called erythrocytosis, means having too many red blood cells, the cells that carry oxygen. On lab tests this shows up as a hemoglobin or hematocrit above what is expected for age and sex. That number does not always mean the same thing, so the first question is whether the red cell mass is truly increased.
When red cell mass really is increased, the clue is erythropoietin, a hormone the kidney releases when cells are short of oxygen. That hormone reaches the erythroid progenitors, the cells that red blood cells come from, and pushes them to make more.
There is one form with a name of its own: polycythemia vera. In nearly 95% of cases there is an acquired mutation called V617F in the JAK2 gene. Its manifestations come from hyperviscosity: too many red blood cells make the blood thicker.
In brief
Polycythemia, or erythrocytosis, is an increase in red cell mass, seen as a hemoglobin or hematocrit elevated for age and sex.
When that mass truly is increased, classification depends on erythropoietin, which the kidney releases in response to cellular hypoxia and which acts on erythroid progenitors.
In polycythemia vera the defect is, in nearly 95% of cases, an acquired JAK2 V617F mutation; its manifestations come from hyperviscosity.
Too many red blood cells make the blood thicker.
Sources (1)
- National Center for Biotechnology Information, StatPearls PublishingPolycythemia, StatPearlsPublished
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
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