Abstract:
Essential thrombocythemia is one of the myeloproliferative syndromes and is characterized by a persistent increase of the platelets > 600 x 109/L. Values can be increased up to 15-fold above normal. The function of the platelets is often impaired and can lead to bleeding and/or thrombosis.
Clinical picture:
On average, the patients are more than 60-years-old at the time of diagnosis. The patients may be asymptomatic and the diagnosis is often established by chance. Symptoms usually result from platelet dysfunction in the microcirculation and manifest themselves in alternating neurologic complaints such as burning sensations of the soles of the foot (erythromelalgia), headaches and dizziness. Arteriolar thrombi lead to acrocyanosis and ischemic damage (e.g. cerebrovascular thrombosis). In patients with increased risk for thromboembolic events, hydroxurea can reduce the frequency of such compliactions. Anagrelide specifically inhibits platelet production in ET.
Hematology:
Platelets are usually markedly elevated (> 600 x 109/L to 1500 x 109/L). Moreover, anisocytosis of the platelets exists; giant platelets and megakaryocyte remnants are seen. Basophilia is typical. Essential thrombocythemia must be distinguished from reactive thrombocytosis (e.g. iron deficiency, solid tumors). Other myeloproliferative syndromes, such as chronic myeloid leukemia for example, must be excluded. The best way of achieving this is by means of bone marrow evaluation.