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
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