Essential thrombocytosis: diagnosis, differential diagnosis, complications and treatment considerations of relevance for a cardiologist.

Essential thrombocytosis (ET) is a rare haematological malignancy, with an incidence rate of 1.5-2.5/100,000 per year. For many patients with ET the first manifestation of their underlying disease is a thrombotic or haemorrhagic complication. A recent retrospective study revealed an incidence rate of at least 2.1% in people under 40 years presenting with an acute coronary syndrome, although the diagnosis was initially missed in all cases. Thus, cardiologists face a much higher than average incidence rate of ET in their daily practice, but seem insufficiently aware of the disease. The current review summarises symptoms, (differential) diagnosis, complications and treatment considerations of ET of relevance for a cardiologist. Typical symptoms, besides thrombosis and haemorrhage, include erythromelalgia and aquagenic pruritus, while platelets > 450 × 10/l are a diagnostic for ET once other myeloproliferative neoplasms, secondary and spurious thrombocytosis have been excluded. With regard to treatment, timing of revascularisation depends on the presence of ischaemia and concurrent platelet counts. In the presence of ischaemia, revascularisation should not be delayed and adequate platelet counts can be achieved by platelet apheresis. In the absence of ischaemia, revascularisation can be delayed until adequate platelet counts have been achieved by cytoreductive therapies. Cardiologists should be aware of/screen for possible ET.