Types of polycythaemia

Increased red cell concentration can be:

• absolute
  • primary - polycythaemia rubra vera - primary defect in the marrow stem cell population causing erythrocytosis irrespective of physiological needs
  • secondary - normal marrow stem cells respond to elevated erythropoietin or erythropoietin-like substances in the blood, however appropriate
    • congenital e.g. - Chuvash erythrocytosis (VHL gene mutation), high oxygen-affinity haemoglobin
    • acquired e.g. - hypoxia driven, pathologic erythropoietin production or exogenous erythropoietin
  • idiopathic - no cause for erythrocytosis can be identified, in this group around one third will have lower erythropoietin levels than normal and the rest have inappropriately normal levels for elevated haemoglobin or raised erythropoietin (2)
• apparent - normal or minimally raised red cell volume with a reduced plasma volume

Reference:

• (1) McMullin MF et al. Guidelines for the diagnosis, investigation and management of polycythaemia/erythrocytosis. Br J Haematol. 2005;130(2):174-95
• (2) McMullin MF. The classification and diagnosis of erythrocytosis. Int J Lab Hematol. 2008;30(6):447-59