Essential thrombocythemia: past and present.
Essential thrombocythemia (ET) is a clonal myeloproliferative disorder characterized by sustained increase in platelet number and tendency for thromboembolism. A somatic point mutation that causes a constitutive activation of the JAK2 gene is found in one in two ET patients. ET is more common in women, its incidence being 0.6-2.5/100,000 patient/year and the median age at diagnosis is 65-70 years. ET can affect all age groups, including children (0.09 cases/year), and is often diagnosed in the third-fourth decade of life. Rare cases of familial ET have been reported. Miscarriages are 3-4 times more common among women with ET than in the general population, especially in patients carrying JAK2V617F. Microvascular disturbances are typical of ET, but a major thrombosis (2/3 arterial and 1/3 venous; 1, 2-3% patient/year) is the main cause of morbidity and mortality. Age over 60 years and/or previous thrombosis are validated risk factor for thrombosis. Hemorrhages occur in 0.33% patient/year, mainly in those with a platelet count over 1,500 x 10(9)/L. Progression to myelofibrosis and leukemia is more common in patients carrying the JAK2V617F mutation, and is estimated to occur in 0.16% and 0.12% patient/year, respectively. The ET-related mortality ratio with respect to the general population is 1:1, while for polycythemia vera it is 1.6:1. Low-dose aspirin is useful for microvascular disturbances, and in the primary and secondary prevention of major thrombosis in high-risk patients, but it is not recommended in patients with a platelet count over 1,500 x 10(9)/L. Hydroxyurea is used as first-line treatment in high-risk patients. Other drugs available are alpha-interferon, anagrelide, pipobroman and busulphan.
Fabris
Fabrizio
F
Department of Medical and Surgical Sciences, University of Padua Medical School, Via Giustiniani 2, 35128 Padua, Italy. fabrizio.fabris@unipd.it
Randi
Maria Luigia
ML
D000368:Aged; D001792:Blood Platelets; D005260:Female; D049673:History, 20th Century; D049674:History, 21st Century; D006801:Humans; D053614:Janus Kinase 2; D008297:Male; D013920:Thrombocythemia, Essential / Q000175:diagnosis / Q000188:drug therapy / Q000453:epidemiology / Q000266:history / Q000503:physiopathology
C507924:JAK2 protein, human; D053614:Janus Kinase 2