[Essential thrombocythemia as critical stroke risk factor--case report].

One of the haematological causes of stroke is essential thrombocythemia (ET). It is one of the proliferative syndromes of the haematopoietic system. Patients with ET have an increased risk of thrombosis and/or haemorrhage of veins and arteries. The patient aged 58 had a history of two stroke incidents within two month despite the treatment with acenocumarole for chronic atrial fibrillation. The clinical diagnostic procedure revealed an increased platelet count was 668 000/ml, and these cerebrovascular events were the first manifestation of ET Antithrombotic drugs were not effective in the secondary prevention of stroke while antiplatelets prevented this patient from further ischemic events for 12 months.