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.
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.
Following is a list of primary and secondary causes of erythrocytosis.
Secondary etiologies are much more common 1:
- erythropoietin receptor (EPOR) mutations
- polycythemia vera
- genetic (LNK) mutations
- high oxygen affinity haemoglobins
- >100 mutations described
- abnormal 2,3 bisphosphoglycerate mutase
- dysfunctional oxygen-sensing pathway
- e.g. VHL mutations
- central hypoxia
- local renal hypoxia
Pathological EPO secretion
- drug administration (physician-directed or illicit)
- 1. McMullin MF. Investigation and Management of Erythrocytosis. (2016) Current hematologic malignancy reports. 11 (5): 342-7. doi:10.1007/s11899-016-0334-1 - Pubmed
- 2. McMullin MF. Congenital erythrocytosis. (2016) International journal of laboratory hematology. 38 Suppl 1: 59-65. doi:10.1111/ijlh.12506 - Pubmed
- 3. Johansson PL, Safai-Kutti S, Kutti J. An elevated venous haemoglobin concentration cannot be used as a surrogate marker for absolute erythrocytosis: a study of patients with polycythaemia vera and apparent polycythaemia. (2005) British journal of haematology. 129 (5): 701-5. doi:10.1111/j.1365-2141.2005.05517.x - Pubmed