Overview of Erythrocytosis

Overview

• Erythrocytosis is the presence of increased circulating red blood cells.
• The terms erythrocytosis and polycythaemia are often used interchangeably, though polycythaemia is less specific as it suggests pathology in multiple cell lineages.

• • Look For

  • Increased red cell count (RCC)
  • Elevated haemoglobin (Hb)
  • Elevated haematocrit (HCT) / packed cell volume (PCV)

• • Interpretation

  • Elevated Hb / PCV with elevated RCC - absolute erythrocytosisBone marrow pathology (primary) or excess erythropoietin (secondary)
  • Elevated Hb / PCV with normal RCC - relative erythrocytosisContraction of plasma volume

• • Causes of Erythrocytosis

  • Primary

  • Primary familial erythrocytosis (EPO receptor mutation)
  • Polycythaemia vera (JAK2 mutation)

  • Secondary

  • Chronic hypoxia - smoking, chronic lung disease, obstructive sleep apnoea, high altitude
  • Renal hypoxia - renal artery stenosis, polycystic kidney disease, post renal transplant
  • Drugs - testosterone, anabolic steroids, erythropoietin
  • Paraneoplastic syndrome (EPO-producing tumour)
  • Congenital - haemoglobinopathies, other mutations
  • Idiopathic

  • Relative

  • Severe dehydration