Polycythaemia

Key points

• Polycythaemia may be relative, primary (polycythaemia rubra vera) or secondary Relative causes
• stress: Gaisbock syndrome Primary
• polycythaemia rubra vera Secondary causes
• obstructive sleep apnoea
• excessive erythropoietin: cerebellar haemangioma, hypernephroma, hepatoma, uterine fibroids* To differentiate between true (primary or secondary) polycythaemia and relative polycythaemia red cell mass studies are sometimes used.