Erythrocytosis

Dr Daniel J Bell et al.

Erythrocytosis (or polycythemia) is the presence of an excessive number of red blood cells in the circulation. It can be primary or arise secondarily to another pathology.

Definition

Absolute erythrocytosis is defined as a red cell mass which is >125% predicted for sex and age 2.

Although the diagnosis of erythrocytosis is often put forward when the hemoglobin and/or hematocrit are elevated, they can both be raised, especially the former, yet the red cell mass not be abnormal. Nevertheless if the hematocrit is >0.60 in men or 0.56 in women, then an absolute erythrocytosis is certain 3.

Causes

Following is a list of primary and secondary causes of erythrocytosis.
Secondary etiologies are much more common 1:

Primary 
Congenital
  • erythropoietin receptor (EPOR) mutations
Acquired
Secondary
Congenital
  • high oxygen affinity haemoglobins
    • >100 mutations described
  • abnormal 2,3 bisphosphoglycerate mutase
  • methemoglobinemia
  • dysfunctional oxygen-sensing pathway
    • e.g. VHL mutations
Acquired

Hypoxia-driven

Pathological EPO secretion

Exogenous EPO

  • drug administration (physician-directed or illicit)
    • erythropoietin
    • androgens

 

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Article information

rID: 60101
System: Haematology
Section: Gamuts
Synonyms or Alternate Spellings:
  • Polycythemia
  • Secondary polycythaemia
  • Secondary polycythemia
  • Secondary erythrocytosis
  • Compensatory erythrocytosis
  • Compensatory polycythaemia
  • Compensatory polycythemia
  • Polycythaemia

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