Abstract: Objective To analyze clinical data of the essential thrombocytosis (ET) children diagnosed with gene mutation testing, and therefor to figure out the clinical features of the disease in childhood and the natural process of disease.Methods A retrospective analysis was conducted in ET patients diagnosed with gene mutation testing and treated in our hospital during Jan.2013 to Dec.2017. Results Nine patients (5 males and 4 females with a median age of 10 years) were diagnosed.Hemorrhage occurred in 1 cases(11.1%),microthrombus in 4 cases (44.4%),and asymptomatic in 4 cases (44.4%).Splenomegaly 3 cases (33.3%) at the course of 30 (7-90) days. The median platelet count at diagnosis was 1117(861-1 614)×10⁹/L, The median white blood cell (WBC) count was 11.62×10⁹/L(9.9-18.61)×10⁹/L, and the median hemoglobin (HB) count was 133(115-150)g/L. Hepatosplenomegaly occurred in 3cases (33.3%). JAK2V617F(+) was the most common mutation type (66.7%) of ET, followed by CALR(+) (22.2%) and MPL(+) (11.1%).There was no significant difference between the clinical manifestations and laboratory indicators of JAK2V617F. The patients were treated with combination of hydroxyurea, interferon, and aspirin. No serious hemorrhage and thrombosis occurred in the patients. No one was evolved any other hematologic diseases at followed-up time ranged from 4-52 months (the median 8 months). Conclusion Primary thrombocytosis disease in children is rare, which is prone to occur in the older. The clinical symptom is not obvious, but positive JAK2V617 mutations are common in specific gene mutation detection. No severe complications and disease progression and transformation occur in a certain period. Large and long-term follow-up data are needed to confirm this conclusion.

Key words: pediatric, essential thrombocytosis, clinical, gene mutation testing