[Clinical analysis of 438 patients with essential thrombocythemia]

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

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

Four 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.

ET 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.