Life-threatening thrombotic complications of relative polycythaemia.

Relative polycythaemia refers to raised haematocrit with normal red cell mass. Plasma volume may be reduced. This condition is associated with acute hypoxia, smoking, alcohol and diuretics. We describe two life-threatening thrombotic events in two patients with relative polycythaemia under age 40 years. The first had myocardial infarction and on admission haemoglobin was 21.6 g dL-1. The second developed pulmonary embolism and haemoglobin was 19.1 g dL-1. Both patients received antithrombotic measures and isovolumetric venesection. Sixteen patients (age <40 years) who attended our accident and emergency department in 1 year had a haemoglobin level of >18.0 g dL-1. Recognition of relative polycythaemia in at risk-individuals may help reduce thrombotic risk.