OBJECTIVETo analyse the clinical feature and natural course of essential thrombocythemia (ET).

METHODSA retrospective analysis was conducted in ET patients treated in our hospital during May 1980 to December 2006.

RESULTSFour hundred and thirty eight patients (201 males and 237 females with a median age of 48 years) were diagnosed. Hemorrhage occurred in 101 cases (23.1%), thrombosis in 86 cases (19.6%), and both hemorrhage and thrombosis in 13 cases (3.0%). Splenomegaly occurred in 150 cases and hepatomegaly occurred in 60 cases. One hundred and forty-nine cases (34%) had no symptoms at diagnosis and 145 cases (33.1%) confirmed by routine blood tests due to other diseases. The median platelet count at diagnosis was 1000 x 10(9)/L [(533 -3740) x 10(9)/L]. Bone marrow biopsy was performed in 255 cases which showed mainly increase of enlarged mature megakaryocytes with hyper-lobulated nuclei and local proliferation of reticular fiber was revealed in 51 cases. JAK2V617F mutation was detected in 90(78.9%) of 114 patients studied. Karyotype analysis was performed in 180 cases and 6 (3.3%) had clonal chromosomal aberrations. Two hundred and sixty-one patients were followed up over 12 months with a median of 60 months (range from 12 to 300 months). Seventeen cases (6.5%) evolved into marrow fibrosis (MF) and one case into polycythemia vera (PV). One case evolved into PV 6 years and then MF 20 years after diagnosis of ET. Three cases developed acute monocyte leukemia (M5), myelodysplastic syndrome (MDS) and multiple myeloma (MM), respectively.

CONCLUSIONSET is a chronic myeloproliferative disorder characterized predominantly by thrombocytosis and hemorrhage. The percentage of asymptomatic cases is high. The prognoses for most cases were good with a few cases may evolve into MF.